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Special Issue "Gallium Nitride-Based Devices"

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A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D：Materials and Processing".

Deadline for manuscript submissions: closed (25 April 2023) | Viewed by 7463

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Special Issue Editor

Dr. Neha Aggarwal

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Guest Editor

Paul-Drude-Institut für Festkörperelektronik, Hausvogteipl. 5-7, 10117 Berlin, Germany
Interests: gallium nitride; aluminium nitride; AlGaN; boron nitride; nanoplasmonics; molecular beam epitaxy of III-nitride material system; optoelectronics; device fabrication; photodetectors

Special Issue Information

Dear Colleagues,

The escalating demand for high-frequency and high-power operations in power conversion systems is leading the way towards a material that should be able to out-perform conventional Si-based components. Gallium Nitride (GaN) is an III-V group compound that is being merged with pre-existing silicon-based semiconductor technology to speed up its accessibility to large-scale users. GaN-based devices have been growing rapidly and have already shown marked importance in solid-state lighting applications, making them high-power and high-speed, especially in the ultraviolet (UV) range due to their wide and direct bandgap properties. With the increasing need to save energy, GaN is an important semiconductor material that possesses the capability to increase technological requirements quite efficiently. The different polarity/orientations of GaN have resulted in a debate regarding its device applicability. Presently, non-polar GaN-based structures are demonstrating higher efficiencies and a faster switching response in UV optoelectronic devices. However, in polar GaN, N-polar portrays the key characteristics of an efficient photodetection device over Ga-polar devices. More recently, atomically thin GaN has emerged and is potentially suitable for ultracompact electronics and optics. This freshly synthesized two-dimensional (2D) GaN allows for control over light-emitting properties guided by strong quantum confinement. Moreover, 2D GaN materials can also act as possible electrode materials for batteries since they have a very low mass density and are definitely an environmentally friendly alternative that can provide high-storage capacities. This Special Issue creates an opportunity for researchers who are willing to contribute to all of these latest material developments and process advancements in GaN technology in the form of research papers, short communications, and perspectives as well as review articles.

We are looking forward to receiving your submissions!

Regards,
Dr. Neha Aggarwal
Guest Editor

Manuscript Submission Information

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Keywords

epitaxial growth
electronic transport
gallium nitride
non-polar GaN
nanostructures
optoelectronics
polarity
radiation-resistant
strain-free growth
semiconductor device technology
UV technology
wide-bandgap
2D semiconductors

Published Papers (7 papers)

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Research

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Open AccessArticle

Revealing the Mechanism of the Bias Temperature Instability Effect of p-GaN Gate HEMTs by Time-Dependent Gate Breakdown Stress and Fast Sweeping Characterization

and

Micromachines 2023, 14(5), 1042; https://doi.org/10.3390/mi14051042 - 12 May 2023

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Abstract

The bias temperature instability (BTI) effect of p-GaN gate high-electron-mobility transistors (HEMTs) is a serious problem for reliability. To uncover the essential cause of this effect, in this paper, we precisely monitored the shifting process of the threshold voltage (V_TH) of HEMTs under BTI stress by fast sweeping characterizations. The HEMTs without time-dependent gate breakdown (TDGB) stress featured a high V_TH shift of 0.62 V. In contrast, the HEMT that underwent 424 s of TDGB stress clearly saw a limited V_TH shift of 0.16 V. The mechanism is that the TDGB stress can induce a Schottky barrier lowering effect on the metal/p-GaN junction, thus boosting the hole injection from the gate metal to the p-GaN layer. This hole injection eventually improves the V_TH stability by replenishing the holes lost under BTI stress. It is the first time that we experimentally proved that the BTI effect of p-GaN gate HEMTs was directly dominated by the gate Schottky barrier that impeded the hole supply to the p-GaN layer. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Open AccessArticle

InGaN Laser Diodes with Etched Facets for Photonic Integrated Circuit Applications

Krzysztof Gibasiewicz

and

Micromachines 2023, 14(2), 408; https://doi.org/10.3390/mi14020408 - 09 Feb 2023

Cited by 1 | Viewed by 903

Abstract

The main objective of this work is to demonstrate and validate the feasibility of fabricating (Al, In) GaN laser diodes with etched facets. The facets are fabricated using a two-step dry and wet etching process: inductively coupled plasma—reactive ion etching in chlorine, followed by wet etching in tetramethylammonium hydroxide (TMAH). For the dry etching stage, an optimized procedure was used. For the wet etching step, the TMAH temperature was set to a constant value of 80 °C, and the only variable parameter was time. The time was divided into individual steps, each of 20 min. To validate the results, electro-optical parameters were measured after each step and compared with a cleaved reference, as well as with scanning electron microscope imaging of the front surface. It was determined that the optimal wet etching time was 40 min. For this time, the laser tested achieved a fully comparable threshold current (within 10%) with the cleaved reference. The described technology is an important step for the future manufacturing of photonic integrated circuits with laser diodes integrated on a chip and for ultra-short-cavity lasers. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Open AccessArticle

Monolithic 45 Degree Deflecting Mirror as a Key Element for Realization of 2D Arrays of Laser Diodes Based on AlInGaN Semiconductors

Kiran Saba

Anna Kafar

Jacek Kacperski

Krzysztof Gibasiewicz

and

Micromachines 2023, 14(2), 352; https://doi.org/10.3390/mi14020352 - 31 Jan 2023

Viewed by 976

Abstract

In this study, we propose a solution for realization of surface emitting, 2D array of visible light laser diodes based on AlInGaN semiconductors. The presented system consists of a horizontal cavity lasing section adjoined with beam deflecting section in the form of 45° inclined planes. They are placed in the close vicinity of etched vertical cavity mirrors that are fabricated by Reactive Ion Beam Etching. The principle of operation of this device is confirmed experimentally; however, we observed an unexpected angular distribution of reflected rays for the angles lower than 45°, which we associate with the light diffraction and interference between the vertical and deflecting mirrors. The presented solution offers the maturity of edge-emitting laser technology combined with versatility of surface-emitting lasers, including on-wafer testing of emitters and addressability of single light sources. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Open AccessArticle

Improved Optical and Electrical Characteristics of GaN-Based Micro-LEDs by Optimized Sidewall Passivation

and

Micromachines 2023, 14(1), 10; https://doi.org/10.3390/mi14010010 - 21 Dec 2022

Cited by 1 | Viewed by 895

Abstract

GaN-based Micro-LED has been widely regarded as the most promising candidate for next generation of revolutionary display technology due to its advantages of high efficiency, high brightness and high stability. However, the typical micro-fabrication process would leave a great number of damages on the sidewalls of LED pixels, especially for Micro-LEDs, thus reducing the light emitting efficiency. In this paper, sidewall passivation methods were optimized by using acid-base wet etching and SiO₂ layer passivation. The optical and electrical characteristics of optimized Micro-LEDs were measured and analyzed. The internal quantum efficiency (IQE) of Micro-LED was increased to 85.4%, and the reverse leakage current was reduced down to 10⁻¹³ A at −5 V. Optimized sidewall passivation can significantly reduce the non-radiative recombination centers, improving the device performance and supporting the development of high-resolution Micro-LED display. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Open AccessArticle

Miniature Mesa Extension for a Planar Submicron AlGaN/GaN HEMT Gate Formation

Moath Alathbah

and

Khaled Elgaid

Micromachines 2022, 13(11), 2007; https://doi.org/10.3390/mi13112007 - 18 Nov 2022

Viewed by 1423

Abstract

In this letter, a novel approach is presented to overcome issues in AlGaN/GaN high electron mobility transistors (HEMTs), such as metal discontinuity of the gate stemmed from conventional mesa isolation. This usually requires a careful mesa etch process to procure an anisotropic mesa-wall profile. An alternative technique is the use of ion implantation for device isolation instead of conventional mesa for a planar device formation. However, ion implantation is a costly process and not always easily accessible. In this work, the proposed method is to simply extend the mesa below the gate just enough to accommodate the gatefeed, thereby ensuring the entire gate is planar in structure up to the gatefeed. The newly developed device exhibited no compromise to the DC (direct current) and RF (radio frequency) performance. Conversely, it produced a planar gate configuration with an enhanced DC transconductance (approximately 20% increase is observed) and a lower gate leakage while the etch process is considerably simplified. Similarly, the RF transconductance of proposed device (device B) increased by 80% leading to considerable improvements in RF performance. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Open AccessArticle

Analysis of Operational Characteristics of AlGaN/GaN High-Electron-Mobility Transistor with Various Slant-Gate-Based Structures: A Simulation Study

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Micromachines 2022, 13(11), 1957; https://doi.org/10.3390/mi13111957 - 11 Nov 2022

Cited by 1 | Viewed by 868

Abstract

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by applying a slant-gate structure and drain-side extended field-plate (FP) for improved breakdown voltage. Prior to the analysis of slant-gate-based HEMT, simulation parameters were extracted from the measured data of fabricated basic T-gate HEMTs to secure the reliability of the results. We suggest three different types of slant-gate structures that connect the basic T-gate electrode boundary to the 1st and 2nd SiN passivation layers obliquely. To consider both the breakdown voltage and frequency characteristics, the DC and RF characteristics of various slant-gate structures including the self-heating effect were analyzed by TCAD simulation. We then applied a drain-side extended FP to further increase the breakdown voltage. The maximum breakdown voltage was achieved at the FP length of 0.4 μm. Finally, we conclude that the slant-gate structures can improve breakdown voltage by up to 66% without compromising the frequency characteristics of the HEMT. When the drain-side FP is applied to a slant-gate structure, the breakdown voltage is further improved by up to 108%, but the frequency characteristics deteriorate. Therefore, AlGaN/GaN HEMTs with an optimized slant-gate-based structure can ultimately be a promising candidate for high-power and high-frequency applications. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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Review

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Open AccessReview

A Brief Overview of the Rapid Progress and Proposed Improvements in Gallium Nitride Epitaxy and Process for Third-Generation Semiconductors with Wide Bandgap

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Micromachines 2023, 14(4), 764; https://doi.org/10.3390/mi14040764 - 29 Mar 2023

Viewed by 939

Abstract

In this paper, we will discuss the rapid progress of third-generation semiconductors with wide bandgap, with a special focus on the gallium nitride (GaN) on silicon (Si). This architecture has high mass-production potential due to its low cost, larger size, and compatibility with CMOS-fab processes. As a result, several improvements have been proposed in terms of epitaxy structure and high electron mobility transistor (HEMT) process, particularly in the enhancement mode (E-mode). IMEC has made significant strides using a 200 mm 8-inch Qromis Substrate Technology (QST^®) substrate for breakdown voltage to achieve 650 V in 2020, which was further improved to 1200 V by superlattice and carbon-doped in 2022. In 2016, IMEC adopted VEECO metal-organic chemical vapor deposition (MOCVD) for GaN on Si HEMT epitaxy structure and the process by implementing a three-layer field plate to improve dynamic on-resistance (R_ON). In 2019, Panasonic HD-GITs plus field version was utilized to effectively improve dynamic R_ON. Both reliability and dynamic RON have been enhanced by these improvements. Full article

(This article belongs to the Special Issue Gallium Nitride-Based Devices)

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