• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.30-30
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• 1996

• Proceedings of the Optical Society of Korea Conference
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• 1997.08a
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• pp.46-46
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• 1997

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.134-140
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• 2010

We have investigated the contactless electroreflectance (CER) properties of $In_{0.5}(Ga_{1-x}Al_x)_{0.5}P$/GaAs double heterostructures grown by metal-organic chemical vapour deposition (MOCVD). The CER measurements on the sample were studied as a function of temperature, modulation voltage ($V_{ac}$), and dc bias voltage ($V_{bias}$). Five signals observed at room temperature are related to the GaAs, $In_{0.5}Ga_{0.5}P$, $In_{0.5}(Ga_{0.73}Al_{0.27})_{0.5}P$, $In_{0.5}(Ga_{0.5}Al_{0.5})_{0.5}P$, and $In_{0.5}(Ga_{0.2}Al_{0.8})_{0.5}P$ transitions, respectively. From the temperature dependence of CER spectrum, the Varshni coefficients and broadening parameters were determined and discussed. In addition, we found that the behavior of the CER amplitude for the reverse bias is larger than that of the forward.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.333-333
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• 2016

현재까지 가장 높은 광전류 변환 효율을 나타내는 III-V 화합물 반도체의 다중접합 태양전지 대신 이보다 단순한 에피구조를 가진 단일셀 이종접합구조의 태양전지를 제안하였다. 이를 한국나노 기술원에서 MOCVD(Metalorganic Vapour Phase Epitaxy) 장비를 이용하여 에피구조를 성장하고 태양 전지를 제작해 그 특성을 조사하였다. 태양 전지는 서로 다른 orientation의 두 GaAs 기판에 각각 동일한 에피 구조로 성장되었다. GaAs 기판은 Si 도핑된 n-type 기판으로 (100) 표면이 <111>A 방향으로 2도 off 된 웨이퍼와 10도 off 된 웨이퍼가 사용되었다. 연구에서 시뮬레이션에 사용된 태양전지의 에피 구조는 맨 위 p-GaAs (p-contact 층), p-InAlP, p-InGaP의 광흡수층과 N-InAlGaP 층과 아래의 n-InAlP와 n-GaAs의 n-contact층으로 이루어져있다.태양전지는 $5mm{\times}5mm$의 면적을 가지고 있다. 그림 1은 전류-전압의 측정된 결과를 나타낸 그래프이다. 태양전지는 1 sun 조건하에서 probe를 이용해 측정되었다. 2도 off GaAs 기판 위에 성장시킨 태양전지에서는 3.7mA의 단락전류값이, 10도$^{\circ}$ off 인 샘플에서는 4.7mA의 단락전류값이 측정되었다. 반면에 전류-전압곡선으로부터 얻은 10도 off 인 태양전지의 직렬 저항값은 2도 off 인 태양전지의 약4배 정도로 나타났다. 이는 기판의 결정방향에 따라 태양전지의 내부 전하 transport에 차이가 있음을 나타낸다. TLM (Transmission Line Model) 방법에 의한 p-contact의 ohmic저항 측정에서도 이와 일치하는 결과를 얻었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.207-210
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• 2001

Metal-organic VPE (MOVPE) epitaxial growth procedure and related device fabrication technique are reported for GaInP-based epitaxial materials and devices. For GaInP/GaInAs two-dimensional electron-gas field-effect transistor (TEGFET), a promising epitaxial stacking structure resulting in enhanced electron mobility is given. In conjunction with this, a new device fabrication technique to improve luminous intensity of GaInP-based LED is also shown.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.164-165
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• 2005

The dry etch characteristics of GaAs over both AlGaAs and InGaP in planar inductively coupled $BCl_3$-based plasmas(ICP) with additions of $SF_6$ or $CF_4$ were studied. The additions of flourine gases provided enhanced etch selectivities of GaAs/AlGaAs and GaAs/InGaP. The etch stop reaction involving formation of involatile $AlF_3$ and $InF_3$ (boiling points of etch products: $AlF_3\sim1300^{\circ}C$, $InF_3$ > $1200^{\circ}C$ at atmosphere) were found to be effective under high density inductively coupled plasma condition. Decrease of etch rates of all materials was probably due to strong increase of flourine atoms in the discharge, which blocked the surface of the material against chlorine neutral adsorption. The process parameters were ICP source power (0 - 500 W), RF chuck power (0 - 30 W) and variable gas composition. The process results were characterized in terms of etch rate, selectivities of GaAs over AlGaAs and InGaP, surface morphology, surface roughness and residues after etching.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.1
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• pp.30-39
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• 1991

The influence of physical parameters (Al mole fraction, thickness, doping concentration) in the window and emitter on the efficiency characteristics of heteroface p-$Al_{x}Ga_{1-x}As/p-GaAs/n-GaAs/n^{+}$-GaAs solar cell is investigated. The maximum efficiency theoretically calculated in this device is obtained when a thickness of the window is in a range of (400-1000))$\AA$and a thickness/doping concentration of the emitter is in a range of (0.5-0.8)$\mu$m/(1-7)${\times}10^{17}cm^{-3}$, respectively. Also is the efficiency improved according to the increase of Al mole fraction in the indirect gap window(0.41${\le}x{\le}1.0$). The optimum designed heteroface cell with an area of 0.165cm$^2$fabricated using MOCVD exhibits an active area conversion efficiency of 17%, having a short circuit current density of 21.2mA/cm\ulcorner an open circuit voltage of 0.94V, and a fill factor of 0.75 under ELH-100mW/cm$^2$illumination.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.104-111
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• 1998

The InGaAs/InP quantum wells(QWs) were grown by low pressure metalorganic chemical vapor deposition and the effects of growth interruption steps on their interfacial structures were investigated by measuring photoluminescence spectra. When InP or InGaAs surface was treated under the same group V ambient, the full width at half maximum (FWHM) of the QW peak increased possibly due to the incorporation of impurities during the growth interruption time. When InP surface was treated under $AsH_3$, howerer, the PL peak showed red-shift due to the As-P exchange reaction and the change of FWHM was not remarkable. The effective thickness of InAs interfacial layer formed during $AsH_3$, treatment on the InP surface was calculated to be 1~2 monolayers. In the case of InGaAs treatment under $PH_3$, the PL peak energy and the FWHM increasied. This results suggest that $PH_3$ treatment on the InGaAs surface suppresses the incorporation of As into the subsequent InP layer and the local replacement of As by P occurs simultaneously.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.12
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• pp.1656-1662
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• 1988

Auger depth profiles of various In Ga As P/In P heterojunctions grown by liquid phase epitaxial techniques under different growth conditions such as diffusion temperature, diffusion time and dopants, have been obtained. The surface contaminations of In Ga As have been investigated. We found that the samples with Zn diffusion exhibit significant interface grading phenomena including In depletion, Ga richness and P richness at the In Ga As P/In P interface, and In outdiffusion at the surface. The main surface contamination was found to be due to carbon and oxygen species. It can be suggested that Zn gettering takes a major role in such phenomena as interface grading, in depletion, and Ga and P richness at the interface.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.29.1-29.1
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• 2009

Fabrication of good quality P-type GaN remained as a challenge for many years which hindered the III-V nitrides from yielding visible light emitting devices. Firstly Amano et al succeeded in obtaining P-type GaN films using Mg doping and post Low Energy Electron Beam Irradiation (LEEBI) treatment. However only few region of the P-GaN was activated by LEEBI treatment. Later Nakamura et al succeeded in producing good quality P-GaN by thermal annealing method in which the as deposited P-GaN samples were annealed in N2 ambient at temperatures above $600^{\circ}C$. The carrier concentration of N type and P-type GaN differs by one order which have a major effect in AlGaN based deep UV-LED fabrication. So increasing the P-type GaN concentration becomes necessary. In this study we have proposed a novel method of activating P-type GaN by electrochemical potentiostatic method. Hydrogen bond in the Mg-H complexes of the P-type GaN is removed by electrochemical reaction using KOH solution as an electrolyte solution. Full structure LED sample grown by MOCVD serves as anode and platinum electrode serves as cathode. Experiments are performed by varying KOH concentration, process time and applied voltage. Secondary Ion Mass Spectroscopy (SIMS) analysis is performed to determine the hydrogen concentration in the P-GaN sample activated by annealing and electrochemical method. Results suggest that the hydrogen concentration is lesser in P-GaN sample activated by electrochemical method than conventional annealing method. The output power of the LED is also enhanced for full structure samples with electrochemical activated P-GaN. Thus we propose an efficient method for P-GaN activation by electrochemical reaction. 30% improvement in light output is obtained by electrochemical activation method.