Mechanical Properties and Creep Behavior of Undoped and Mg-Doped GaN Thin Films Grown by Metal–Organic Chemical Vapor Deposition
Round 1
Reviewer 1 Report
The paper is devoted to investigation of mechanical properties of Mg-doped and undoped GaN layers. The GaN is a very important material for power electronics and light-emitting diodes applications. It's mechanical properties are indeed of high importance, thus the paper would be interesting for the technologists involved into GaN fabrication.
The paper is mostly well organized and conclusions are justified. Only some small remarks can be made to improve the paper structure and specify the English for some of the phrases.
1) Introduction lines 20-21, the sentence "This study represents..." is actually repeating the earlier phrase.
2) Line 42 "among others" is repeating the idea already mentioned at the beginning of the sentence.
3) Line 81-82 "Mg doped GaN layer was grown at 1100°C and deposited on the GaN buffer layer and then followed by annealing in N2 environment gas". If GaN was grown it annot be further deposited. Please check the idea of the sentence and the grammar.
4) Line 120 hc must be specified directly after formula (2);
5) Formula (6), please check "k.G"
1) Line 49 "literature suggests that there is limited research" please check the construction, might be mistakenous.
2) Line 57 "... more research", I haven't ever encountered such construction, please check if it is correct.
3) Line 85-86 "The thickness of the undoped and Mg doped GaN layers was approximately 2 μm", maybe (The thicknesses of the undoped and Mg doped GaN layers was approximately 2 μm for each).
4) Line 159 "Previous studies reported that in highly Mg doped GaN rough films grown by MOCVD process" - the sentence might be correct but not clear for understanding;
5) Line 181 "...were analyzed and are presented..." I'm not sure if it is correct to present two different tenses in one sentence.
Author Response
he response to Reviewer#1 is attached in PDF format.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
A. Chauhan et al. report the mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown on sapphire substrates using MOCVD with TMG and Cp2Mg as the precursors for Ga and Mg, respectively. Overall, the idea received my attention and the methodology is technically sound. However, there are some specific issues the authors should address by making modifications before we can proceed and positive action can be taken.
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The title is the part of a paper that is read the most and is usually read first. It is, therefore, the most important element that defines the research study. Avoid language, such as, "A Study to Investigate the…," or "An Examination of the…". These phrases are obvious and generally superfluous unless they are necessary to covey the scope, intent, or type of a study. Therefore, just using “Mechanical Properties and Creep Behavior of Undoped and Mg-doped GaN Thin Films grown by MOCVD” as the title is recommended.
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When you use an abbreviation in both the abstract and the text, define it in BOTH places upon first use. Further, after you define an abbreviation, use only the abbreviation. Do not alternate between spelling out the term and abbreviating it. i.e., TMG, LED…
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Please increase the font size in Fig. 1 to ensure that all micrographs have scale markers, and all scale markers and text in figures are large enough to be easily read.
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The results and discussion section can be divided into several subsections rather than presented in a huge section.
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The authors investigated the properties of the undoped and Mg-doped GaN. Have the authors noticed some papers documenting these points and experimental methods using precursors? i.e., [Strain-enhanced properties of van der Waals heterostructure based on blue phosphorus and g-GaN as a visible-light-driven photocatalyst for water splitting. RSC Adv. 2019, 9, 4816–4823, doi:10.1039/C8RA09378D], [Magnetic behaviors of 3d transition metal-doped silicane: a first-principle study. J. Supercond. Nov. Magn. 2018, 31, 2789–2795, doi:10.1007/s10948-017-4532-4], and [Switching behavior of a heterostructure based on periodically doped graphene nanoribbon. Phys. Rev. Appl. 2021, 16, 024030, doi:10.1103/PhysRevApplied.16.024030]…
Author Response
The response to Reviewer#2 is attached in PDF format.
Author Response File: Author Response.pdf
Reviewer 3 Report
some questions and suggestions to authors,
1. A full name of each acronym should be added in the revised manuscript, even in the title and abstract.
2. Detailed information on each analysis instrument should be described in the revised manuscript.
3. Can the Mg mapping on the GAN substance be shown?
4. I suggest showing the XRD pattern of the sample.
Author Response
The response to Reviewer#3 is attached in PDF format.
Author Response File: Author Response.pdf
Reviewer 4 Report
The submitted manuscript dealed with mechanical properties of GaN and Mg-doped GaN. This research is important in industrial fields. I have some following comments for publication.
1. Figure 1: These are difficult to see labels of axis of SPM images. So the scale is not clear.
2. L383-386: The transition from n-type to p-type conductivity with increasing in Mg concentration was described. But there were no result of electrical properties in the manuscript.
English is acceptable.
Author Response
The response to Reviewer#4 is attached in PDF format.
Author Response File: Author Response.pdf
Reviewer 5 Report
The current paper reports the investigation on mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown by MOCVD. The major criticism of the paper is that, there is so many claims regarding dislocation, point defects, fracture toughness, transition from n-type to p-type conductivity etc., without any proof against the claims. The authors need to address these areas, without which, it will not be possible to accept the paper. Based on that, I recommend major revision of the manuscript. The specific comments are as follows:
1. Line 17: Introduce the full form before start using abbreviation.
2. Try to incorporate key quantitative results in the abstract.
3. The analytical background section is well established in literature. Thus, this section may either completely removed or at least shorten with due references.
4. Line 167 and beyond: The claims regarding dislocation is crucial and required experiments proof, at least as supplementary materials. Otherwise, this claims are not acceptable.
5. Line 291 and beyond: Again, there is a claim regarding fracture toughness, without any proof? Did the author calculated K1c values? If not, then what is the justification of the claims?
6. In the whole paper there is no SEM/TEM images regarding the structure/thickness of the coatings, which is highly recommended.
7. The authors claimed the thickness of the film is about 2 um. What is the proof/origin of that claim?
8. Did the authors measure the residual stress of the coating? For these type of coating and involved deposition method, formation of residual stress is very common, that influence the coatings’ mechanical properties sin a large scale.
9. The proofs towards the claims regarding dislocations, pint defects, fracture toughness is must!
10. Line 386: “a transition from n-type to p-type conductivity” where is the proof? There is no data regarding that in the whole manuscript!
Minor editing of English language required
Author Response
The response to Reviewer#5 is attached in PDF format.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
No more questions.
Reviewer 5 Report
Accept in present form
