Analysis of Key Factors for Green Supplier Selection: A Case Study of the Electronics Industry in Vietnam

: In recent years, green supply chain management (GSCM) and green supplier selection (GSS) have become signiﬁcant trends and have received increasing attention around the globe and in Vietnam. This research aimed to explore the key factors for GSS in the case of the electronics industry in Vietnam. Modiﬁed Delphi and analytic hierarchy process (AHP) methods were used to determine the factors and measure their importance, with data collected from experts in Vietnam’s electronics industry. According to the analytical results, the ranking of importance of ﬁve dimensions for selecting green suppliers was product quality, cost and service performance, environmental management, technology capability, and supplier risks. Key factors for GSS included the capability of handling abnormal quality, product price, quality assurance, quality-related certiﬁcates and lead time. These research ﬁndings could help electronics companies in Vietnam and other developing countries to make strategic decisions when selecting suppliers and offer guidance for suppliers on increasing their competitive advantages. Additionally, this study provides a comprehensive overview picture of environmental management and GSCM implementation to the government.


Introduction
With the advancement in mobile communication technology and edge computing management mechanisms, IoT (Internet of Things) applications have become increasingly popular and efficient in building smart cities and providing a green and friendly environment [1].IoT technology has the potential to drive green solutions for the industry and government.Integrating IoT into any viable model of a sustainable global economy is a main trend [2].In recent decades, concern for environmental management has obviously increased due to the fast-paced development of the economy.Many environment-related regulations and institutional pressures have driven enterprises to control environmental risks and threats.The European Union (EU) has applied strict regulations on a reduction in hazardous substances (RoHS Directive) and the waste of electrical and electronic equipment (WEEE Directive).The regulation concerning the registration, evaluation, authorization and restriction of chemicals (REACH) has enforced companies to change their production methods to be more eco-friendly.In 2015, the United Nations General Assembly also set up Sustainable Development Goals (SDGs) with a collection of 17 goals calling for actions to improve a better and more sustainable future around the globe.One of the vital SDGs is to protect the environment and combat climate change and its impacts.Investors and customers also require more environmental, social and corporate governance practices from companies for innovative value chains and environmentally friendly products and services [3].In a survey from Accenture [4], 72% of consumers purchased more environmentally friendly products than five years ago, and 81% of respondents wanted to purchase more in the next five years.To deal with these expectations from stakeholders, regulations from organizations and governments, companies must integrate economic growth and environmental issues to enhance sustainable development.One of the important issues in developing sustainable strategies was building a green supply chain that integrated environmental factors into supply chain management (SCM).For businesses, the "greening" of the supply chain was considered a part of a green investment strategy, helping businesses to effectively use natural and environmentally friendly resources, thereby improving their competitiveness and business performance.To build a green supply chain, businesses had to start by sourcing and choosing green suppliers who provided environmentally friendly materials.Therefore, the key factors for green supplier selection (GSS) were an important research topic worth investigating.
The electronics manufacturing industry occupies a key position that significantly affects the development of other industries.In research from VietnamCredit [5], the electronics industry accounts for 17.8% of the industrial sector of Vietnam.The main products of this industry are electronic components, telephones, telephone components, assembled televisions, tablets, computers, and components, along with office equipment, etc.In 2021, the electronics industry showed continuous growth with an increasing demand for consumer goods and communication tools for work due to the impact of the COVID-19 pandemic.Despite the impact of the pandemic, this industry still showed positive signs in development, with the highest turnover in the recent ten years, and accounted for 30% to 40% of the national gross domestic product (GDP) of Vietnam [6].
Vietnam exports computer products and electronic components around the globe, mainly to the markets of China, the US, ASEAN, Japan, South Korea and the EU (including the Netherlands, Germany, Poland, Finland, and so on) [6].The growth rate of the export turnover of electronic products is quite high but unstable.In addition, domestic enterprises in Vietnam face severe competition with similar products from markets in ASEAN and China.A high increase in value and speed occurred after multinational companies such as Samsung, Intel and Canon put their production factories in Vietnam into operation.According to DIGITIMES Research [7], Samsung Electronics has spearheaded the relocation wave as the global manufacturing industry experienced diversification in previous decades.The huge amount of investment by Samsung in Vietnam beginning in 2016 has created a reciprocal relationship between Samsung and local governments.
In Vietnam, the high export growth of the electronics industry resulted from the "China Plus One" strategy, where multinational technology groups moved production factories out of China to avoid rapidly increasing labor costs [8].With a relative advantage in labor and a favorable geo-economic position, Vietnam has gained great benefits from this process and supplied electronics products to giant markets, including China, the US, and the EU.Despite its great development and potential for expansion, the electronics industry in Vietnam is principally dominated by foreign companies, particularly multinational enterprises.From 2016 to 2020, the number of foreign direct invested (FDI) companies constituted one-third of the total number of Vietnam's electronics companies, but the export contributed to over 90% of the total export turnover and covered 80% of the domestic market demand [9].Samsung, Vietnam's largest single source of FDI, has been a major producer of that country's exports and has a synergistic and symbiotic relationship with Vietnam's national and subnational governments [10].
This study focuses on selecting green suppliers in the electronics industry in Vietnam.Vietnam has the advantage of abundant human resources, with 68.6% of people at working age (15-64) [11] and competitively low labor costs.Therefore, Vietnam has great potential to attract investment capital from countries around the world.In the period 2011-2020, the electronics industry experienced considerable development due to the increasing foreign direct investment (FDI) projects in the electronics area.On average, the index of manufacturing electronic products, computers, and their parts increased by 28.6% during this period.In 2019, the export value of electronic goods, computers and their parts reached 36.3 billion USD and became Vietnam's second-largest group of exported goods in 2019 [12].
Although Vietnam has achieved this great growth and is among the 12th largest electronics exporters in the world and ranks third in ASEAN, about 95% of the value belongs to FDI enterprises [13].A breakthrough is essential to support Vietnamese domestic companies in the electronics industry to continue growing by participating in the global value chain.To achieve this goal, the competitiveness of the SCM should be enhanced, especially through an appropriate supplier selection process.The awareness and execution of the GSS process could enable Vietnamese domestic enterprises to build their sustainable SCM, connect with multinational corporations, and participate in the global value chain in the electronics industry.
To adopt this global trend, the Ministry of Industry and Trade in Vietnam has implemented the National Action Program on sustainable production and consumption to 2020, with a vision extending to 2030, including the execution of "Greening the distribution system and developing the supply chain of environmentally friendly products and services" [6].As one of the main industries in the manufacturing sector of Vietnam, it is important for electronics companies to apply environmental practices in their production under the guidance of the government.
Vietnam's electronics manufacturing has been selected as one of five supply chains in the joint intervention "Sustainable Supply Chains to Build Forward Better to promote decent work for a sustained, sustainable and justifiable recovery from the COVID-19 crisis" implemented by the EU and the International Labor Organization (ILO).It is urged that the country apply and develop its sustainable supply chain in electronics manufacturing, with being more environmentally responsible as one of the main focuses.
Since the GSS process enables Vietnamese domestic enterprises to build their sustainable SCM, the aim of this research is to explore, understand and evaluate the key factors for the GSS process in electronic companies in Vietnam.Existing studies on GSS problems are redundant and much research has discussed GSS problems in different industries.However, to our best knowledge, rare studies in the literature have analyzed the GSS criteria for the electronics industry in Vietnam.This study aims to fill some of the gaps in the existing literature.In addition, many countries are now suffering from the deadly pandemic COVID-19, which has created considerable negative impacts on global economic development; the GSCM and GSS, therefore, are greatly affected and need to be adjusted to deal with this new problem.Since few studies have investigated this problem, this paper focuses on analyzing the key factors for the GSS process in the electronics industry in Vietnam and in the context of the COVID-19 outbreak's impact.The findings of the study can provide a comprehensive picture of the GSS of Vietnamese electronics enterprises.The contributions of this paper include:

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The creation of a framework for GSS in the electronics industry; • Determining and evaluating the factors influencing the GSS of Vietnamese electronics enterprises; • Suggesting the implementation of environmental practices for sustainable development to electronics companies in Vietnam and other developing countries.

Literature Review 2.1. Environmental Management and Green Supply Chain Trend
The environment is of particular importance to the existence and development of human life and the economic, cultural and social development of every country and the globe.The environmental pollution caused by human activities is becoming more serious and directly threatens sustainable socio-economic growth.Therefore, solving environmental pollution problems in the period of accelerating industrialization and modernization has been one of the most concerning issues.To maintain a green and sustainable environment, businesses are not just stopping at complying with international regulations such as RoHS, WEEE, REACH, ERP, ELV, etc., but are also making a great effort to implement environmental protection programs voluntarily as a competitive strategy in the current economic development context.Businesses can gradually move toward the new supply chain trend-GSCM [14].
Since the early 1990s, manufacturers have faced pressures to become more environmentally conscious of their SCM [15].When "green" is added to SCM, the concept of GSCM can be defined as a method to reduce a product's or service's environmental impact, including all stages of a product's life cycle from raw material sourcing, design, production and distribution to the final consumer and how they use the product.GSCM involves traditional SCM practices integrating environmental standards or concerns into procurement decisions and long-term relationships with suppliers.It is associated with the management of the whole chain, including green design, GSS, internal government management practices, collaboration with customers for green purchasing, and resource recovery [16].
GSS is considered to be the most critical function of GSCM since it contributed to the improvement guarantee of both product quality and environmental protection [17].With the increasing popularity of GSCM trends in the world and the awareness of environmental issues, enterprise procurement not only focuses on evaluating the quality, price and lead time of a product but puts more concerns on the environmental impact of a product.A company that desires long-term and sustainable success must consider both financial aspects and environmental factors in supplier selection.Diabat and Govindan [18] pointed out that the adoption of green procurement from GSCM has helped businesses to achieve a leading position in this market.
The COVID-19 pandemic has caused unprecedented challenges in the global business environment.Multinational companies have faced a raw material supply and demand shock as many countries impose isolation and social distancing orders to control the spread of the pandemic.In that context, the challenge for businesses is how to connect and maintain supply chain operations to meet domestic production and consumption needs and, at the same time, increase the value of export goods.Enterprises need to improve COVID-19 prevention and control measures in their operations, develop production and business activities as well as import and export under this new global situation.To minimize the damage from the unpredictable risks of the COVID-19 pandemic, enterprises need to develop a GSCM with resilience [19].

Recent Research on GSS
Supplier selection plays a significant part in SCM and contributes to the success of business organizations.Choosing suitable green suppliers and managing them is the basis for organizations to minimize their input costs, enhance the quality of goods and services provided to customers, and improve their competitiveness in the global market.Many studies have proposed different research models on GSS in various industries.
Lee et al. [20] combined the Delphi and Fuzzy extended AHP methods to evaluate the criteria for GSS in the case of a TFT-LCD manufacturing company in Taiwan.The Delphi method was utilized to select both traditional and green criteria.Then, the fuzzy extended AHP method was applied to determine the importance of those criteria and also solve the vagueness of experts' opinions.Lu et al. [21] studied the criteria for the selection of green suppliers in the straw biomass industry.A cloud model was used to solve the randomness and vagueness of evaluation information, and the fuzzy AHP was utilized to evaluate the importance degree of criteria for GSS.This research has considered various factors, including economy, delivery capability, fuel quality, and environment in the GSS process, and taken the straw biomass industry in China as the case study.Liou et al. [17] combined the DEMATEL, D-ANP and modified COmplex PRoportional ASsessment of alternatives with Grey relation (COPRAS-G) methods to solve the dependent relationship between criteria, the fuzziness information and diverse opinions from experts to improve the evaluation of GSS, in the context of a Taiwanese electronics company.
Gao et al. [22] proposed a group consensus decision-making framework, which combined the paired comparison method and the consistency measure to address the consensus problem of GSS in the electronics industry.To reach a consensus, the experts were asked to revise their judgment based on a feedback mechanism in each round.Lo et al. [23] utilized a model integrating the best-worst method (BWM), modified fuzzy technique for order preference by similarity to an ideal solution (TOPSIS), and fuzzy multi-objective linear programming (FMOLP) to address the green supplier evaluation and order allocation problem, with the data from an electronics manufacturer in Taiwan.Deshmukh and Sunnapwar [24] evaluated the importance of criteria for GSS in the Indian industry considering seven main practices, including quality, environmental performance, green manufacturing, customer operation, green cost, green design, and green logistics design.In the paper, experts were asked to weigh the degree of importance for each criterion in pairwise comparisons, and then the AHP method was applied to obtain the final results.
Mabrouk [25] utilized fuzzy rules to interpret the experts' qualitative knowledge of key factors for GSS into numerical data.In this study, green R&D, eco-design, green image, green packaging, and remanufacturing were determined to be the top factors for GSS.Freeman and Chen [26] considered both traditional and environmental factors to analyze the factors for GSS.Based on the analysis of data from a Chinese electronic machinery company, research results indicated that senior managers still ranked traditional criteria more highly than environmental criteria.Kannan et al. [27] adopted the fuzzy AHP and fuzzy technique to evaluate green suppliers and a multi-objective linear programming (MOLP) model with which to solve the problem of order allocation among selected suppliers considering their constraints.An automobile manufacturer was considered to illustrate the proposed model.Kannan et al. [28] also analyzed the green supplier evaluation in a Brazilian electronics company by utilizing the fuzzy TOPSIS method and Spearman rank correlation coefficient.Based on the rankings obtained, the influences of criteria were examined, and the key criteria indicated the commitment of senior management to GSCM as the most important one.Kuo et al. [29] studied the importance and relationship of criteria for GSS, considering both environmental and management dimensions.The environmental performance of suppliers was also evaluated using the VIKOR method, and then a solution for each criterion was provided accordingly.
Mousakhani et al. [30] proposed a new model combining the compromise ranking method and interval type-2 fuzzy sets (IT2FSs) to address the GSS problems in the case of a battery company in Iran.Sensitivity analysis was applied to study the influences of experts' weights on criteria rankings.Qin et al. [31] developed the interactive multi-criteria decision-making (MCDM) method to solve the multiple criteria group decision-making (MCGDM) problems for GSS in the interval type-2 fuzzy sets (IT2FSs) environment in the case of the automobile industry.Yu and Hou [32] utilized a modified multiplicative analytic hierarchy process (MMAHP) method to select the most suitable green suppliers for an automobile manufacturer.This method also proved that rankings were maintained when a new supplier was added.Ðalić et al. [33] used the Fuzzy PIvot Pairwise RElative Criteria Importance Assessment (fuzzy PIPRECIA) method to identify the criteria for GSS.The Interval Rough Simple Additive Weighting (SAW) was integrated to find out the best alternative considering environmental criteria.
In the research of Chiou et al. [34], the GSS among American, Japanese and Taiwanese electronics companies in China was analyzed and compared.There were six criteria with 24 sub-criteria chosen and evaluated by the Fuzzy AHP (FAHP) method, and the supply chain-based criterion ranked the highest in all three countries.Javad et al. [35] focused on determining the key criteria for GSS and evaluating their green performance by applying BWM and fuzzy TOPSIS methods, with the consideration of suppliers' green innovation abilities.Sensitivity analysis was also used to handle biases in the research results.Büyüközkan and Çifçi [36] examined the interdependent relationships within as well as among groups of criteria to provide a more accurate analysis of GSS and evaluation.A framework that integrated the fussy DEMATEL, fuzzy ANP and TOPSIS methods were applied, and GSS evaluation was based on the data from a company in Turkey.To evaluate the green suppliers in the coffee bean supply chain in Vietnam, Nguyen et al. [37] adopted a combined model of FAHP and VIKOR, considering both environmental and conventional factors, which were identified based on literature review and experts' confirmation.The findings indicated that the quantity discount, solid waste generation, order fulfillment rate, logistics cost, and purchasing costs were the most critical factors for GSS.
Existing studies on GSS problems are redundant, and many research methods (such as AHP, Delphi, TOPSIS, etc.) have been adopted to address GSS problems in different industries.However, to our best knowledge, no study has analyzed GSS criteria for the electronics industry in Vietnam.In addition, many countries are now suffering from the deadly pandemic COVID-19, which has created considerable negative impacts on global economic development, including the GSCM and GSS; therefore, these criteria are greatly affected and need to be adjusted to deal with this new problem.Since few studies have investigated this problem, this paper focused on analyzing the key factors for the GSS process in the electronics industry in Vietnam in the context of COVID-19's outbreak impact.
Recently, Ghosh et al. [38] proposed a GSCM framework for real-world supplier selection problems.Their results indicated that "total energy consumption", "total scrap material generation", and "renewable energy utilization" are the main influential parameters for GSS.Ecer [39] utilized an extension of the AHP model to better deal with ambiguity and vagueness and to solve supplier selection problems involving green concepts.The results from a case of a home appliance manufacturer indicate that the most important factors in selecting green suppliers were cleaner production, energy/material saving, green package, remanufacturing, and an environmental management system.Tsai et al. [40] explored these obstacles when organizations implemented GSCM practices.They found that organizational changes had the most critical impact.Khattak et al. [41] developed a multi-objective interactive fuzzy programming model considering a green appraisal score, cost, quality, and time for GSS.

Selection of GSS Criteria
Combining this with the criteria for GSS reviewed in the previous section, this study adopted seven dimensions and 26 criteria that affect GSS in Vietnamese electronics companies.Table 1 lists the definitions of the dimensions and criteria considered in this research.

Criteria Definition Reference
Product cost

Product price
The production costs, such as the processing cost, maintenance cost and warranty cost.[22,27,42] Logistic cost Sum of lengthy distribution channel costs, transportation costs, handling and packaging costs, inventory costs, damage and insurance costs required during transportation.[21,22,27,28] Quantity discount Reduction in material cost based on purchase quantity.[27,37] Product quality

Quality-related certificate
Whether supplier has quality-related certificates (ISO 9000, QS 9000, etc.) to ensure that it has a certified quality management system.[20,25,32] Quality assurance Whether suppliers carried out quality assessments on parts, whether they are certified for strict quality assurance and have a strong commitment to preventing quality failures.[22,42] Handling abnormal quality capability The capability of the supplier to solve abnormal quality problems.[20,42] Reject rate The number of parts rejected due to certain quality problems detected by incoming quality control and the production line.[22,27,37] Table 1.Cont.

Lead time
The amount of time from the placement to the arrival of an order.[21,27,34] On-time delivery The capability to meet delivery schedules.[21,26] Order fulfillment rate The capability of the supplier to comply with the predetermined order quantity.[27,37]

Responsiveness
The ability to change according to the demand of customers, price structure, and the frequency of orders.

Technology level
The technology development level to meet company's current and future demands.[20,22,27] Capability of R&D The ability to research and develop to satisfy current and future demands of the company.[20,34,43] Capability of design The ability of new product designs to satisfy current and future demands of the company.[20,22,27] Remanufacturing capability The ability to reuse and repair components to rebuild a new product.[25,26,34] Environmental management

Waste management
The quantity control and treatment of waste by the supplier.[29,34] Environment-related certificates Whether the supplier has relevant environment management certifications (such as ISO 14000).[22,25,26] Hazardous substances control The control of chemicals and hazardous materials used in production.[17,29,34] Energy consumption control The control of the amount of energy used in production.[20,25,32,37] Green product

Recycling
The level to recycle products.[20,33,43] Eco-design The capability to improve product design for products to be more environmentally friendly.[34,42] Green packaging The use of green materials in packaging reduces their energy consumption and negative impacts on the environment.

Financial stability
The financial status of the supplier ensures they have a resilient financial system.[23,32,36] Social responsibility The integration of the supplier's social and environmental concerns into their business operations.[20,32,37]

Rule and regulation compliance
The compliance level of the supplier to government rules and regulations, customers' requirements and environmental standards.[17,20,28,34] Risk assessment and risk management capability The ability to identify and evaluate the risks and implement appropriate practices for controlling identified risks. [29]

Methods
This research analyzes and discusses the key factors for the GSS process by interviewing several experts in the electronics industry.The Delphi method is commonly used in group decision-making processes.This study adopted a Modified Delphi method to reach a consensus on the critical criteria for the GSS process among the panelists.Then, the AHP process broke down complex decisions into smaller, more manageable parts before comparing them to each other in a pairwise fashion and was used to determine the importance of those criteria.

Modified Delphi Method
The Delphi method was developed by Dalkey and Helmer [44] in the 1950s and has been widely used to collect data from groups of experts.The characteristic feature of this method is that experts are surveyed in several rounds and know nothing about the other participants.With the parameters and multi-round structure given to the expert panel of the Delphi method, the results obtained in each round are fed back in the next round until a consensus is reached or the purpose of the study is satisfied.
To select the best green suppliers, many economic and environmental criteria needed to be considered during the evaluation process.This study adopted the Modified Delphi method to confirm the validity of GSS criteria in the case of the electronics industry in Vietnam.First, a panel of experts was selected so that they had expertise and experience in evaluating and selecting suppliers or had experience in material purchasing.The experts listed in Table 2 had 5 to 21 years of work experience in the electronics industry.With the difference in the number of years of work experience, experts could give a comprehensive perspective on the factors for GSS.After selecting the expert panel, a questionnaire was conducted to collect the experts' opinions.The implementation of the Modified Delphi method consists of two rounds of a semi-closed survey:

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Round 1: Experts are asked to determine the factors affecting GSS in electronics companies in Vietnam by grading their importance based on a five-level Likert scoring scale and explain their selection and suggestions for adjusting the criteria mentioned in the survey.

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Round 2: The questionnaire is revised based on experts' suggestions and comments and is re-sent to them with the summary and analysis of answers in round 1.Experts are asked to re-evaluate the criteria considering other panelists' opinions.
After two rounds of the survey, and based on the common consensus of experts, the critical criteria for GSS are determined and then evaluated in the next stage.

Analytic Hierarchy Process (AHP)
The AHP method was one of the MCDM methods proposed by Saaty in the late 1970s.AHP is a mixture of quantitative and qualitative methods that are used to evaluate alternatives based on the given criteria.The AHP method adopts experts' opinions and does not require a huge volume of data for analysis.The AHP method was performed through the following six steps: Step 1: Define the problems and develop the objectives.
Step 2: Build a hierarchical structure with the top level as the research goal or the problem to be solved.Subsequent levels should include key components or standards.The bottom level is the variant level, which contains the alternatives placed below their direct criteria.
Step 3: Construct a pairwise comparison matrix A of size n × n = (a ij ), in which i runs in rows, j runs in columns, and matrix A is extracted from the survey results collected from the expert panel.
In a pairwise comparison matrix, one element is the inverse of the corresponding symmetric element in relation to the diagonal element, that is, a ijj = 1/a ij .The decision maker needs to give his/her assessment of the importance of each criterion relative to the others to the higher-level standard of the hierarchy using the pairwise comparison method.The importance scale is taken on a nine-point Saaty scale.
Step 4: Calculate the relative weights of the decision elements by the Eigenvector Method (EM).The normalized pairwise matrix can be obtained by summing the values by column, then dividing each value of the matrix by the total value of the corresponding column.The sum of each column now equals 1.After that, the normalized weights of the criteria w = (w 1 , w 2 , w 3 , . . .w n ) can be calculated by averaging across the rows of the weighted normalized pairwise matrix A.
Step 5: Calculate the consistency index (CI) to evaluate the quality of the pairwise comparison matrix.
The difference expressed as λ max − n can be used to measure the inconsistency.Full consistency occurs when λ max − n = 0.The AHP method uses the consistency ratio (CR) CR = CI/RI as a measure of inconsistency independent of the order of the matrix, where RI is the random index suggested by Saaty [45].Based on empirical studies, Saaty suggested that the acceptable value of CR should be smaller than or equal to 0.1.
Step 6: Aggregate the relative weights to obtain an overall rating for alternatives and make a final decision.

Framework for GSS
The Modified Delphi method can be conducted with a two-round questionnaire to determine the framework for GSS.In the first round, a list of dimensions and criteria obtained from the literature review is sent to five selected experts.All of them have responses to their degree of agreement and suggestions for dimensions and criteria.The threshold for an average agreement degree in this round is 75%.Based on the panelists' evaluation, the criteria "Logistics cost", "Quantity discount", "On-time delivery", "Waste management" and "Eco-design" should be removed since the average agreement degrees of these five criteria are all lower than the threshold.This means these five criteria were not the main factors for selecting a green supplier.The experts also suggest integrating the "Green product" dimension into the "Environmental management" dimension and combining the "Product cost" and "Delivery and Service performance" dimensions into a new dimension named "Cost and Service performance".After the first round, five dimensions and 21 criteria were confirmed in the framework.In the second round, with the collected results and suggestions from the panelists, the survey was revised and resent to five experts for re-evaluation.The threshold for the average agreement degree on criteria was 85% in the second round.All participants in the panel reached a consensus to maintain five dimensions and 21 criteria with an average agreement degree higher than 85%.After two rounds of the questionnaire, the formal hierarchical structure for GSS was determined and indicated in Figure 1.

Participant Demographics
The AHP survey was distributed to 15 experts who worked in the electronics industry, and all of them responded with complete answers within a three-week period.Since only 12 responses satisfied a consistency ratio smaller than 0.1, the data from 12 qualified responses were analyzed for final results and implications.Experts participating in this survey were all at the management level in the companies.Nine and three experts had 5-10 years and more than 10 years of work experience, respectively, in electronics companies in Vietnam.To be more specific, all of them had work experiences relating to supplier

Participant Demographics
The AHP survey was distributed to 15 experts who worked in the electronics industry, and all of them responded with complete answers within a three-week period.Since only 12 responses satisfied a consistency ratio smaller than 0.1, the data from 12 qualified responses were analyzed for final results and implications.Experts participating in this survey were all at the management level in the companies.Nine and three experts had 5-10 years and more than 10 years of work experience, respectively, in electronics companies in Vietnam.To be more specific, all of them had work experiences relating to supplier evaluation and selection, including six experts from the material purchasing team, three from the supplier quality engineering team, two experts from the new product introduction team, and one from the operations program management team.

Importance Evaluation of Dimensions and Criteria
Five dimensions were determined and evaluated for their importance with pairwise comparison in the AHP method.These dimensions included both traditional factors and green factors of supplier selection.Based on the analytical results, the priority of dimensions for GSS included product quality (0.39073), cost and service performance (0.30072), environmental management (0.17062), technology capability (0.08361), and supplier risks (0.05432).
The criteria in each dimension were also evaluated with a pairwise comparison to determine the influential degree of each criterion for GSS in the electronics industry in Vietnam.Based on the analytical results, the average local weight of the criteria in each dimension was obtained, and the local rankings were determined accordingly.Table 3 lists the local weights and rankings of each criterion.For product quality dimensions, according to experts, an abnormal quality handling capability (0.35885) was the most influential criterion and the reject rate (0.15591) was the least concerning criterion.In the cost and service performance dimension, the final score showed that product price (0.45723) played the most important part in evaluating a green supplier for electronics companies.Considering the technology capability dimension, the most critical concern of electronics firms for GSS was R&D capability (0.44478) and remanufacturing capability (0.11987), which was relatively less important than other criteria in this dimension.For the environmental management dimension, most respondents agree that energy consumption control (0.25973) is the most important criterion which decides the green factor of suppliers.Recycling (0.23476) and hazardous material management (0.22750) are also relatively important criteria when determining the environmentally friendly level of suppliers.In supplier risk dimensions, the factors with the highest priority were rule and regulation compliance (0.35811), and the least important factor for GSS in the Vietnamese electronics industry was risk assessment and risk management capability (0.10610).
A comparison of all 21 criteria in five dimensions was conducted to find out the most critical factor for GSS in electronics companies.Table 4 shows the integrated priority with the global weight and ranking for each criterion.According to the numerical results, the most important criterion is the abnormal quality handling capability with the highest global weight (0.14850).Product price ranks second with a priority of 0.13574, followed by quality assurance (0.10645), quality-related certificate (0.08664) and lead time (0.08313), accordingly.The criterion with the lowest priority was risk assessment and risk management capability (0.00876).According to the rankings of all criteria described in the previous section, many non-environment-related criteria have high priority weights even though the research model is for the selection of green suppliers.After discussing with all experts in the AHP questionnaire, an agreed threshold for determining the critical factors affecting GSS was set as 0.08.Based on the confirmed threshold, the critical factors decided by experts were abnormal quality handling capability, product price, quality assurance, quality-related certificate and lead time.Taking these five criteria into consideration, it could be observed that no environmental criterion existed in the group of key factors, and only three out of five environment-related factors were listed in the top ten.Among these five dimensions, environmental management only ranked third out of five, and product quality and cost and service performance were the two most critical dimensions for GSS.
The analytical results indicate that for evaluating green suppliers in the electronics industry in Vietnam, several traditional criteria are still ranked higher than environmental ones, and no environment-related criterion is among the top five important factors.These results are similar to the results from the GSS research [26,32,37].In developing countries, reducing costs to provide a competitive price is critical if enterprises lack a complex product or technical advantage.Nguyen et al. [37] investigated GSS in the coffee bean supply chain in Vietnam.The most important criterion was "quantity discount", which is also a cost-related factor similar to the second critical factor, "product price", in this study.Although GSCM and GSS have been popular and taken seriously by most organizations and governments in the world, this concept is still new in Vietnam, and the country is in the beginning stage of developing GSCM strategies.Hence, companies and managers need more time to be aware of the importance and benefits of integrating environmental management into their business.Additionally, with the adverse impacts of the COVID-19 pandemic on the economy, for small and medium-sized firms, considering environmental factors in production remains challenging due to the large costs and lack of supportive policies.The research results show that environmental management is still not the top priority of electronics companies in Vietnam.Some practical suggestions listed in the following are provided for companies to increase their concerns and responsibility for environmental issues.

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Enterprises should pay attention to energy-saving and recycled materials and require partners and suppliers to be more conscious about environmental management in their production.The different types of materials used in a product should emphasize recycling and reuse.

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Enterprises should consider green product design and the economical and efficient use of raw materials.This can be achieved not only by the adjustment of input materials but the ability to recycle and reuse products in the future.

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The production process should be eco-friendly by reducing the use of raw materials and energy and, therefore, minimizing the quantity of waste produced.In addition, reducing waste by controlling gas emissions and wastewater with treatment methods, using pollution control equipment, or alternative materials, recycling, and the application of advanced technology in the production process should be considered.Furthermore, the distribution network should have a less negative impact on the environment.

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Enterprises can investigate potential suppliers for environmental concerns, educate suppliers on environmental issues, and emphasize environmental aspects when signing contracts with suppliers and logistics partners.

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Enterprises can educate and orient employees to adhere to environmentally friendly principles.Companies should conduct regular training courses to convey more information about the impacts of environmental issues and climate change on socioeconomic development and human life to increase their responsibility for environmental protection.

Conclusions
The electronics industry plays an important role that significantly affects the economic development of Vietnam.In order to continue growing, Vietnamese domestic companies need to participate in the global value chain.An appropriate supplier selection process is a necessity for building the competitive advantages of SCM.Since many environment-related regulations have driven enterprises to control environmental risks and threats, green supply chain management and green supplier selection have become significant trends.This study investigated the critical factors for GSS and suggested the implementation of environmental practices for sustainable development in electronics companies in Vietnam.
From the analytical results, product quality was determined to be the most significant dimension, while cost and service performance was the second most significant for GSS in an electronics company in Vietnam.Environmental management, technology capability, and supplier risks ranked third, fourth and last, respectively.Considering the criterion level, abnormal quality handling capability, product price, quality assurance, quality-related certificate and lead time were critical criteria that electronics companies were concerned with for selecting suppliers, and the risk assessment and risk management capability was the lowest concern for companies.
Many examples of past research on the selection of green suppliers have not focused on Vietnam's electronics industry which attracts investment from global electronics giants.Through this study, the government and related organizations in Vietnam could gain an insight into the current situation of environmental management in enterprises and produce timely and proper policies to solve arising environmental problems and boost the process of implementing green growth in the country.According to research results, key factors for GSS in the electronics industry in Vietnam are traditional ones, and only three environmental criteria are in the top ten priorities.These results are similar to other GSS research in developing countries.Green suppliers and GSCM are still new concepts in Vietnam's electronics industry.It is essential for enterprises to raise awareness of the importance of environmental management if they want to outperform other competitors.The government and related organizations should give incentives to enterprises for integrating environment-related factors into their business operations.
Although this study has contributed to the understanding of evaluating GSS in the electronics industry, there are still several limitations.This study only focused on GSS in supply chain management.However, other sustainability factors also need to be considered, especially during the outbreak of a pandemic such as COVID-19.Future research should investigate the sustainable supply chain to find out how the pandemic has affected businesses and what the key factors are for sustainable supplier selection in the electronics industry, considering the outbreak of a pandemic.Moreover, due to the limitation of time and resources, the data collected in this research are only from a small group of experts working in the electronics industry.Further studies should consist of a larger sample of experts from more companies and research organizations with topic-related research backgrounds and interests.This would bring a more comprehensive perspective on GSS and lead to the results being more useful for managers and businesses.

Table 1 .
GSS criteria considered in this research.

Table 2 .
Background of expert panel.

Table 3 .
Local weights and rankings of criteria.

Table 4 .
All criteria global weights and rankings.