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10 pages, 4372 KiB

Open AccessArticle

Breakdown Behavior of Metal Contact Positions in GaN HEMT with Nitrogen-Implanted Gate Using TCAD Simulation

by Gene Sheu, Yu-Lin Song, Ramyasri Mogarala, Dupati Susmitha and Kutagulla Issac

Micromachines 2022, 13(2), 169; https://doi.org/10.3390/mi13020169 - 22 Jan 2022

Cited by 1 | Viewed by 4038

In this study, the breakdown behavior of a calibrated depletion mode AlGaN/GaN transistor with a nitrogen-implanted gate region was simulated and analyzed using Sentaurus TCAD simulation, with particular emphasis on the metal contact design rule for a GaN-based high-electron-mobility transistor (HEMT) device with [...] Read more.

In this study, the breakdown behavior of a calibrated depletion mode AlGaN/GaN transistor with a nitrogen-implanted gate region was simulated and analyzed using Sentaurus TCAD simulation, with particular emphasis on the metal contact design rule for a GaN-based high-electron-mobility transistor (HEMT) device with a variety of 2DEG concentrations grown on a silicon substrate. The breakdown behaviors for different source/drain contact schemes were investigated using Sentaurus simulation. The metal contact positions within the source and drain exhibited different piezoelectric effects and induced additional polarization charges for the 2DEG (two-dimensional electron gas). Due to the variation of source/drain contact schemes, electron density has changed the way to increase the electric field distribution, which in turn increased the breakdown voltage. The electric field distribution and 2DEG profiles were simulated to demonstrate that the piezoelectric effects at different metal contact positions considerably influence the breakdown voltage at different distances between drain metal contacts. When the contact position was far away from the AlGaN/GaN, the breakdown voltage of the nitrogen-implanted gated device decreased by 41% because of the relatively low electron density and weak induced piezoelectric effect. This reduction is significant for a 20 μm source-drain length. The minimum critical field used for the breakdown simulation was 4 MV/cm. The simulated AlGaN/GaN device exhibits different breakdown behaviors at different metal contact positions in the drain. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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11 pages, 3032 KiB

Open AccessArticle

Graphene/AlGaN/GaN RF Switch

by Yevhen Yashchyshyn, Paweł Bajurko, Jakub Sobolewski, Pavlo Sai, Aleksandra Przewłoka, Aleksandra Krajewska, Paweł Prystawko, Maksym Dub, Wojciech Knap, Sergey Rumyantsev and Grzegorz Cywiński

Micromachines 2021, 12(11), 1343; https://doi.org/10.3390/mi12111343 - 31 Oct 2021

Cited by 7 | Viewed by 2460

Abstract

RF switches, which use a combination of graphene and two-dimensional high-density electron gas (2DEG) in the AlGaN/GaN system, were proposed and studied in the frequency band from 10 MHz to 114.5 GHz. The switches were integrated into the coplanar waveguide, which allows them [...] Read more.

RF switches, which use a combination of graphene and two-dimensional high-density electron gas (2DEG) in the AlGaN/GaN system, were proposed and studied in the frequency band from 10 MHz to 114.5 GHz. The switches were integrated into the coplanar waveguide, which allows them to be used in any system without the use of, e.g., bonding, flip-chip and other technologies and avoiding the matching problems. The on-state insertion losses for the designed switches were measured to range from 7.4 to 19.4 dB, depending on the frequency and switch design. Although, at frequencies above 70 GHz, the switches were less effective, the switching effect was still evident with an approximately 4 dB on–off ratio. The best switches exhibited rise and fall switching times of ~25 ns and ~17 ns, respectively. The use of such a switch can provide up to 20 MHz of bandwidth in time-modulated systems, which is an outstanding result for such systems. The proposed equivalent circuit describes well the switching characteristics and can be used to design switches with required parameters. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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14 pages, 4374 KiB

Open AccessArticle

Improvement of p-Type AlGaN Conductivity with an Alternating Mg-Doped/Un-Doped AlGaN Layer Structure

by Chi-Chung Chen, Yu-Ren Lin, Yu-Wei Lin, Yu-Cheng Su, Chung-Chi Chen, Ting-Chun Huang, Ping-Hsiu Wu, C. C. Yang, Shin Mou and Kent L. Averett

Micromachines 2021, 12(7), 835; https://doi.org/10.3390/mi12070835 - 18 Jul 2021

Cited by 2 | Viewed by 2922

Abstract

Using molecular beam epitaxy, we prepared seven p-type AlGaN samples of ~25% in Al content, including six samples with Mg-doped/un-doped AlGaN alternating-layer structures of different layer-thickness combinations, for comparing their p-type performances. Lower sheet resistance and higher effective hole mobility are obtained in [...] Read more.

Using molecular beam epitaxy, we prepared seven p-type AlGaN samples of ~25% in Al content, including six samples with Mg-doped/un-doped AlGaN alternating-layer structures of different layer-thickness combinations, for comparing their p-type performances. Lower sheet resistance and higher effective hole mobility are obtained in a layer-structured sample, when compared with the reference sample of uniform Mg doping. The improved p-type performance in a layer-structured sample is attributed to the diffusion of holes generated in an Mg-doped layer into the neighboring un-doped layers, in which hole mobility is significantly higher because of weak ionized impurity scattering. Among the layer-structured samples, that of 6/4 nm in Mg-doped/un-doped thickness results in the lowest sheet resistance (the highest effective hole mobility), which is 4.83 times lower (4.57 times higher) when compared with the sample of uniform doping. The effects of the Mg-doped/un-doped layer structure on p-type performance in AlGaN and GaN are compared. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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9 pages, 4985 KiB

Open AccessArticle

Investigation of 3.3 kV 4H-SiC DC-FSJ MOSFET Structures

by Chia-Yuan Chen, Yun-Kai Lai, Kung-Yen Lee, Chih-Fang Huang and Shin-Yi Huang

Micromachines 2021, 12(7), 756; https://doi.org/10.3390/mi12070756 - 27 Jun 2021

Cited by 4 | Viewed by 2597

Abstract

This research proposes a novel 4H-SiC power device structure—different concentration floating superjunction MOSFET (DC-FSJ MOSFET). Through simulation via Synopsys Technology Computer Aided Design (TCAD) software, compared with the structural and static characteristics of the traditional vertical MOSFET, DC-FSJ MOSFET has a higher breakdown [...] Read more.

This research proposes a novel 4H-SiC power device structure—different concentration floating superjunction MOSFET (DC-FSJ MOSFET). Through simulation via Synopsys Technology Computer Aided Design (TCAD) software, compared with the structural and static characteristics of the traditional vertical MOSFET, DC-FSJ MOSFET has a higher breakdown voltage (BV) and lower forward specific on-resistance (R_on,sp). The DC-FSJ MOSFET is formed by multiple epitaxial technology to create a floating P-type structure in the epitaxial layer. Then, a current spreading layer (CSL) is added to reduce the R_on,sp. The floating P-type structure depth, epitaxial layer concentration and thickness are optimized in this research. This structure can not only achieve a breakdown voltage over 3300 V, but also reduce R_on,sp. Under the same conditions, the Baliga Figure of Merit (BFOM) of DC-FSJ MOSFET increases by 27% compared with the traditional vertical MOSFET. R_on,sp is 25% less than that of the traditional vertical MOSFET. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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16 pages, 4999 KiB

Open AccessArticle

Physics-Based TCAD Simulation and Calibration of 600 V GaN/AlGaN/GaN Device Characteristics and Analysis of Interface Traps

by Yu-Lin Song, Manoj Kumar Reddy, Luh-Maan Chang and Gene Sheu

Micromachines 2021, 12(7), 751; https://doi.org/10.3390/mi12070751 - 26 Jun 2021

Cited by 4 | Viewed by 3437

Abstract

This study proposes an analysis of the physics-based TCAD (Technology Computer-Aided Design) simulation procedure for GaN/AlGaN/GaN HEMT (High Electron Mobility Transistor) device structures grown on Si (111) substrate which is calibrated against measurement data. The presence of traps and activation energies in the [...] Read more.

This study proposes an analysis of the physics-based TCAD (Technology Computer-Aided Design) simulation procedure for GaN/AlGaN/GaN HEMT (High Electron Mobility Transistor) device structures grown on Si (111) substrate which is calibrated against measurement data. The presence of traps and activation energies in the device structure will impact the performance of a device, the source of traps and position of traps in the device remains as a complex exercise until today. The key parameters for the precise tuning of threshold voltage (V_th) in GaN transistors are the control of the positive fixed charges −5 × 10¹² cm⁻², donor-like traps −3 × 10¹³ cm⁻² at the nitride/GaN interfaces, the energy of the donor-like traps 1.42 eV below the conduction band and the acceptor traps activation energy in the AlGaN layer and buffer regions with 0.59 eV below the conduction band. Hence in this paper, the sensitivity of the trap mechanisms in GaN/AlGaN/GaN HEMT transistors, understanding the absolute vertical electric field distribution, electron density and the physical characteristics of the device has been investigated and the results are in good agreement with GaN experimental data. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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9 pages, 3803 KiB

Open AccessArticle

E/D-Mode GaN Inverter on a 150-mm Si Wafer Based on p-GaN Gate E-Mode HEMT Technology

by Li-Fang Jia, Lian Zhang, Jin-Ping Xiao, Zhe Cheng, De-Feng Lin, Yu-Jie Ai, Jin-Chao Zhao and Yun Zhang

Micromachines 2021, 12(6), 617; https://doi.org/10.3390/mi12060617 - 27 May 2021

Cited by 6 | Viewed by 3046

Abstract

AlGaN/GaN E/D-mode GaN inverters are successfully fabricated on a 150-mm Si wafer. P-GaN gate technology is applied to be compatible with the commercial E-mode GaN power device technology platform and a systematic study of E/D-mode GaN inverters has been conducted with detail. The [...] Read more.

AlGaN/GaN E/D-mode GaN inverters are successfully fabricated on a 150-mm Si wafer. P-GaN gate technology is applied to be compatible with the commercial E-mode GaN power device technology platform and a systematic study of E/D-mode GaN inverters has been conducted with detail. The key electrical characters have been analyzed from room temperature (RT) to 200 °C. Small variations of the inverters are observed at different temperatures. The logic swing voltage of 2.91 V and 2.89 V are observed at RT and 200 °C at a supply voltage of 3 V. Correspondingly, low/high input noise margins of 0.78 V/1.67 V and 0.68 V/1.72 V are observed at RT and 200 °C. The inverters also demonstrate small rising edge time of the output signal. The results show great potential for GaN smart power integrated circuit (IC) application. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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9 pages, 1453 KiB

Open AccessArticle

Investigation of Normally-Off p-GaN/AlGaN/GaN HEMTs Using a Self-Terminating Etching Technique with Multi-Finger Architecture Modulation for High Power Application

by Ya-Chun Chang, Yu-Li Ho, Tz-Yan Huang, Ding-Wei Huang and Chao-Hsin Wu

Micromachines 2021, 12(4), 432; https://doi.org/10.3390/mi12040432 - 14 Apr 2021

Cited by 7 | Viewed by 3737

Abstract

Normally-off p-gallium nitride (GaN) high electron mobility transistor (HEMT) devices with multi-finger layout were successfully fabricated by use of a self-terminating etching technique with Cl₂/BCl₃/SF₆-mixed gas plasma. This etching technique features accurate etching depth control and low [...] Read more.

Normally-off p-gallium nitride (GaN) high electron mobility transistor (HEMT) devices with multi-finger layout were successfully fabricated by use of a self-terminating etching technique with Cl₂/BCl₃/SF₆-mixed gas plasma. This etching technique features accurate etching depth control and low surface plasma damage. Several devices with different gate widths and number of fingers were fabricated to investigate the effect on output current density. We then realized a high current enhancement-mode p-GaN HEMT device with a total gate width of 60 mm that exhibits a threshold voltage of 2.2 V and high drain current of 6.7 A. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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Review

Jump to: Research

20 pages, 8321 KiB

Open AccessReview

The Evolution of Manufacturing Technology for GaN Electronic Devices

by An-Chen Liu, Po-Tsung Tu, Catherine Langpoklakpam, Yu-Wen Huang, Ya-Ting Chang, An-Jye Tzou, Lung-Hsing Hsu, Chun-Hsiung Lin, Hao-Chung Kuo and Edward Yi Chang

Micromachines 2021, 12(7), 737; https://doi.org/10.3390/mi12070737 - 23 Jun 2021

Cited by 24 | Viewed by 7261

Abstract

GaN has been widely used to develop devices for high-power and high-frequency applications owing to its higher breakdown voltage and high electron saturation velocity. The GaN HEMT radio frequency (RF) power amplifier is the first commercialized product which is fabricated using the conventional [...] Read more.

GaN has been widely used to develop devices for high-power and high-frequency applications owing to its higher breakdown voltage and high electron saturation velocity. The GaN HEMT radio frequency (RF) power amplifier is the first commercialized product which is fabricated using the conventional Au-based III–V device manufacturing process. In recent years, owing to the increased applications in power electronics, and expanded applications in RF and millimeter-wave (mmW) power amplifiers for 5G mobile communications, the development of high-volume production techniques derived from CMOS technology for GaN electronic devices has become highly demanded. In this article, we will review the history and principles of each unit process for conventional HEMT technology with Au-based metallization schemes, including epitaxy, ohmic contact, and Schottky metal gate technology. The evolution and status of CMOS-compatible Au-less process technology will then be described and discussed. In particular, novel process techniques such as regrown ohmic layers and metal–insulator–semiconductor (MIS) gates are illustrated. New enhancement-mode device technology based on the p-GaN gate is also reviewed. The vertical GaN device is a new direction of development for devices used in high-power applications, and we will also highlight the key features of such kind of device technology. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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19 pages, 3052 KiB

Open AccessReview

Challenges and Advancement of Blue III-Nitride Vertical-Cavity Surface-Emitting Lasers

by Chia-Yen Huang, Kuo-Bin Hong, Zhen-Ting Huang, Wen-Hsuan Hsieh, Wei-Hao Huang and Tien-Chang Lu

Micromachines 2021, 12(6), 676; https://doi.org/10.3390/mi12060676 - 09 Jun 2021

Cited by 8 | Viewed by 4000

Abstract

Since the first demonstration of (Al, In, Ga)N-based blue vertical-cavity surface-emitting lasers (VCSELs) in 2008, the maximum output power (P_max) and threshold current density (J_th) has been improved significantly after a decade of technology advancements. This article reviewed the [...] Read more.

Since the first demonstration of (Al, In, Ga)N-based blue vertical-cavity surface-emitting lasers (VCSELs) in 2008, the maximum output power (P_max) and threshold current density (J_th) has been improved significantly after a decade of technology advancements. This article reviewed the key challenges for the realization of VCSELs with III-nitride materials, such as inherent polarization effects, difficulties in distributed Bragg’s reflectors (DBR) fabrication for a resonant cavity, and the anti-guiding effect due to the deposited dielectrics current aperture. The significant tensile strain between AlN and GaN hampered the intuitive cavity design with two epitaxial DBRs from arsenide-based VCSELs. Therefore, many alternative cavity structures and processing technologies were developed; for example, lattice-matched AlInN/GaN DBR, nano-porous DBR, or double dielectric DBRs via various overgrowth or film transfer processing strategies. The anti-guiding effect was overcome by integrating a fully planar or slightly convex DBR as one of the reflectors. Special designs to limit the emission polarization in a circular aperture were also summarized. Growing VCSELs on low-symmetry non-polar and semipolar planes discriminates the optical gain along different crystal orientations. A deliberately designed high-contrast grating could differentiate the reflectivity between the transverse-electric field and transverse-magnetic field, which restricts the lasing mode to be the one with the higher reflectivity. In the future, the III-nitride based VCSEL shall keep advancing in total power, applicable spectral region, and ultra-low threshold pumping density with the novel device structure design and processing technologies. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor (WBG) Microelectronics and Optoelectronic Devices)

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