• 대한전자공학회논문지SD
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• 제47권6호
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• pp.1-6
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• 2010

본 논문에서는 고출력 고이득 특성을 갖는 고전자이동도 트랜지스터 (high-electron mobility transistor, HEMT)를 구현하기 위하여 계단형 구조의 게이트 전극을 갖는 AlGaN/GaN HEMT를 제안하였고, 소자의 DC 특성의 향상 가능성을 확인하기 위하여 단일 게이트 전극을 갖는 HEMT 및 field-plate 구조의 게이트 전극을 갖는 HEMT 소자와의 특성을 비교 분석하였다. 상용 시뮬레이터를 통해 시뮬레이션 결과, 본 연구에서 제안한 계단형 구조의 게이트 전극을 갖는 AlGaN/GaN HEMT는 드레인 전압의 인가 시, 소자의 내부에서 발생하는 전계가 단일 게이트 전극을 갖는 HEMT에 비해 약 70% 정도 감소하는 특성을 갖는 것을 확인하였고, 전달이득 (transconductance, $g_m$) 특성 역시 단일 게이트 전극구조의 HEMT나 field-plate 구조를 삽입한 HEMT에 비해 약 11.4% 정도 향상된 우수한 DC 특성을 갖는 것을 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.557-565
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• 2014

We report the effect of basal-plane stacking faults (BSFs) on X-ray diffraction (XRD) of non-polar (11$\underline{2}$0) a-plane GaN films with different $SiN_x$ interlayers. Complete $SiN_x$ coverage and increased three-dimensional (3D) to two-dimensional (2D) transition stages substantially reduce BSF density. It was revealed that the Si-doping profile in the Si-doped GaN layer was unaffected by the introduction of a $SiN_x$ interlayer. The smallest in-plane anisotropy of the (11$\underline{2}$0) XRD ${\omega}$-scan widths was found in the sample with multiple $SiN_x$ layers, and this finding can be attributed to the relatively isotropic GaN mosaic resulting from the increase in the 3D-2D growth step. Williamson-Hall (WH) analysis of the (h0$\underline{h}$0) series of diffractions was employed to determine the c-axis lateral coherence length (LCL) and to estimate the mosaic tilt. The c-axis LCLs obtained from WH analyses of the present study's representative a-plane GaN samples were well correlated with the BSF-related results from both the off-axis XRD ${\omega}$-scan and transmission electron microscopy (TEM). Based on WH and TEM analyses, the trends in BSF densities were very similar, even though the BSF densities extracted from LCLs indicated that the values were reduced by a factor of about twenty.

• 전기전자학회논문지
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• 제22권1호
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• pp.205-208
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• 2018

본 연구에서는 상시불통형 p-AlGaN-게이트 질화갈륨(GaN) 이종접합 트랜지스터의 신뢰성 평가를 위한 가속열화 시험 조건을 수립하기 위해 게이트 전압 열화 시험을 진행하였다. 상시불통형 트랜지스터의 동작 조건을 고려하여 기존 상시도통형 쇼트키-게이트 소자평가에 사용되는 게이트 역전압 시험과 더불어 순전압 시험을 수행하여 열화특성을 분석하였다. 기존 상시도통형 소자와 달리 상시불통형 소자에서는 게이트 역전압 시험에 의한 열화는 관찰되지 않은 반면, 게이트 순전압 시험에서 심한 열화가 관찰되었다. 상시불통형 질화갈륨 전력 반도체 소자의 신뢰성 평가에 게이트 순전압 열화 시험이 포함되어야 함을 제안한다.

• 한국결정성장학회지
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• 제25권6호
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• pp.231-238
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• 2015

사파이어 단결정은 GaN계 화합물 증착이 용이하여 고휘도 LED(Light Emitting Diode), 고출력 레이저 산업 등에서 크게 각광받고 있다. 다양한 사파이어 단결정 제조공법 중 vertical Bridgman 공법은 고품질의 사파이어를 c-축 방향으로 성장시킬 수 있는 공법이며 상업적으로 적용이 검토되고 있다. 본 연구에서는 2인치 사파이어 성장 vertical Bridgman 공정에서 성장시 온도구배에 의해 발생하는 열응력을 유한요소 모델을 통해 분석하였다. 이를 통해 성장시 수직, 수평방향으로의 온도구배가 사파이어 결정의 열응력과 결함발생에 미치는 영향을 검토하였다.

• 한국재료학회지
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• 제28권4호
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• pp.208-213
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• 2018

Epitaxial ($11{\bar{2}}0$) a-plane GaN films were grown on a ($1{\bar{1}}02$) R-plane sapphire substrate with photoresist (PR) masks using metal organic chemical vapor deposition (MOCVD). The PR mask with striped patterns was prepared using an ex-situ lithography process, whereas carbonization and heat treatment of the PR mask were carried out using an in-situ MOCVD. The heat treatment of the PR mask was continuously conducted in ambient $H_2/NH_3$ mixture gas at $1140^{\circ}C$ after carbonization by the pyrolysis in ambient $H_2$ at $1100^{\circ}C$. As the time of the heat treatment progressed, the striped patterns of the carbonized PR mask shrank. The heat treatment of the carbonized PR mask facilitated epitaxial lateral overgrowth (ELO) of a-plane GaN films without carbon contamination on the R-plane sapphire substrate. Thhe surface morphology of a-plane GaN films was investigated by scanning electron microscopy and atomic force microscopy. The structural characteristics of a-plane GaN films on an R-plane sapphire substrate were evaluated by ${\omega}-2{\theta}$ high-resolution X-ray diffraction. The a-plane GaN films were characterized by X-ray photoelectron spectroscopy (XPS) to determine carbon contamination from carbonized PR masks in the GaN film bulk. After $Ar^+$ ion etching, XPS spectra indicated that carbon contamination exists only in the surface region. Finally, the heat treatment of carbonized PR masks was used to grow high-quality a-plane GaN films without carbon contamination. This approach showed the promising potential of the ELO process by using a PR mask.

• 한국전자파학회논문지
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• 제26권9호
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• pp.783-789
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• 2015

본 논문에서는 long term evolution(LTE) 통신을 위한 2.6 GHz 대역에서 동작하는 고효율 Doherty 전력증폭기를 설계하였다. 2차 및 3차 고조파 임피던스를 조정하기 위한 간단한 구조의 정합 네트워크를 통해 전력증폭기의 고효율 동작을 달성하였다. Doherty 전력증폭기는 다양한 측면에서 장점을 갖는 GaN-HEMT 소자를 이용하여 제작되었으며, 10 MHz의 대역폭 및 6.5 dB 첨두 전력 대 평균 전력비(PAPR)의 특성을 갖는 LTE downlink 신호를 이용하여 측정되었다. 평균 전력 33.4 dBm에서 13.1 dB의 전력 이득, 57.6 %의 전력부가효율(PAE) 및 -25.7 dBc의 인접채널누설비(ACLR) 특성을 갖는다.

• 한국전자파학회논문지
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• 제28권9호
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• pp.685-697
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• 2017

본 논문에서는 탐색 레이다에서 사용되는 C-대역의 고출력전력증폭장치 및 구성품의 설계, 제작과 측정에 대하여 기술하였다. 반도체 소자인 GaN(질화갈륨)을 적용하여 반도체전력증폭조립체를 설계 및 제작하였고, 설계 제작된 도파관 형태의 송신신호결합조립체를 통해 병렬로 구성된 반도체전력증폭조립체의 송신신호 출력을 결합하여 고출력 송신신호 출력을 발생한다. 제작된 고출력전력증폭장치는 C-대역 500 MHz 대역폭, 최대 10.5 % 듀티, 송신펄스폭 $0.0{\sim}000{\mu}s$에서 송신출력 44.98 kW(76.53 dBm) 이상이다.

• Transactions on Electrical and Electronic Materials
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• 제18권1호
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• pp.7-12
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• 2017

This work takes place in the context of the development of a transport phenomena simulation based on group III nitrides. Gallium and boron nitrides (GaN and BN) are both materials with interesting physical properties; they have a direct band gap and are relatively large compared to other semiconductors. The main objective of this paper is to study the effect of boron content on the electron transport of the ternary compound $B_xGa_{(1-x)}N$ and the effect of the temperature of this alloy at x=50% boron percentage, specifically the piezoelectric, acoustic, and polar optical scatterings as a function of the energy, and the electron energy and drift velocity versus the applied electric field for different boron compositions ($B_xGa_{(1-x)}N$), at various temperatures for $B_{0.5}Ga_{0.5}N$. Monte carlo simulation, was employed and the three valleys of the conduction band (${\Gamma}$, L, X) were considered to be non-parabolic. We focus on the interactions that do not significantly affect the behavior of the electron. Nevertheless, they are introduced to obtain a quantitative description of the electronic dynamics. We find that the form of the velocity-field characteristic changes substantially when the temperature is increased, and a remarkable effect is observed from the boron content in $B_xGa_{(1-x)}N$ alloy and the applied field on the dynamics of holders within the lattice as a result of interaction mechanisms.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.280-280
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• 2014

We report the fabrication and electroluminescent characteristics of GaN/InxGa1-xN microdonut-shaped light-emitting diode (LED) microarrays as variable-color emitters. The diameter, width, height, and period of the GaN microdonuts were controlled by their growth parameters and the geometrical factors of the growth mask patterns. For the fabrication of microdonut LEDs, p-GaN/p-AlxGa1-xN/u-GaN/u-InxGa1-xN heteroepitaxial layers were coated on the entire surface of n-GaN microdonuts. The microdonut LED arrays showed strong light emission, which could be seen with the unaided eye under normal room illumination. Additionally, magnified optical images of microdonut LED arrays exhibited microdonut-shaped light emissions having spatially resolved blue and green colors. Their electroluminescence spectra had two dominant peaks at 460 and 560 nm. With increasing applied voltage, the intensity of the blue emission peak increased much faster than that of the green emission peak, indicating that the color of the LEDs is tunable. We also demonstrated that EL spectra of the devices could be controlled by changing the size of microdonut LEDs. What we want to emphasize here with the microdonut LEDs is that they have additional inner sidewall facets which did not exist for other typical three-dimensional structures including nanopyramids and nanorods, and that InxGa1-xN single quantum well formed on the inner sidewall facets had unique thickness and chemical composition, which generated additional EL color. The origin of the electroluminescence peaks was investigated by structural characterizations and chemical analyses.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권3호
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• pp.109-113
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• 2005

It has been reported that the failure phenomenon and variation of electrical characteristic due to the effect of electrostatic discharge(ESD) in silicon devices. But we had fess reports about the phenomenon due to the ESD in the compound semiconductors. So there are a lot of difficulty to the phenomenon analysis and to select the protection method of main circuits or the devices. It has not been reported that the relation between the ESD stress and GaN devices, which is remarkable to apply the operation in high temperature and high voltage due to the superior material characteristic. We studied that the characteristic variation of the AlGaN/GaN HEMT current, the leakage current, the transconductance(gm) and the failure phenomenon of device due to the ESD stress. We have applied the ESD stress by transmission line pulse(TLP) method, which is widely used in ESD stress experiments, and observed the variation of the electrical characteristic before and after applying the ESD stress. The on-current trended to increase after applying the ESD stress. The leakage current and transconductance were changed slightly. The failure point of device was mainly located in middle and edge sides of the gate, was considered the increase of temperature due to a leakage current. The GaN devices have poor thermal characteristic due to usage of the sapphire substrate, so it have been shown to easily fail at low voltage compared to the conventional GaAs devices.