• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.294-300
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• 2006

We fabricated the distributed feedback (DFB) InP/InGaAs/InP grating structures on InP (100) substrates by metal-organic chemical vapor deposition, and their structural properties were investigated by atomic force microscopy and scanning electron microscopy. Self-assembled InAs/InAlGaAs quantum dots (QDs) were grown on the InP/InGaAs/InP grating structures by molecular beam epitaxy, and their optical properties were compared with InAs/InAlGaAs QDs without grating structure. The duty of the grating structures was about 30%. The PL peak position of InAs/InAlGaAs QDs grown on the grating structure was 1605 nm, which was red-shifted by 18 nm from that of the InAs/InAlGaAs QDs without grating structure. This indicates that the formation of InAs/InAlGaAs QDs was affected by the existence of the DFB grating structures.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.9
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• pp.64-71
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• 1997

A new etching technique of meltback was investigated for GaAs lensed optical devices with selective windows opending in the LPE (liquid phase epitaxy) system. In the meltback process, the etch depth and the etch shape were controlled by the degree of under-saturation, etch time and other parameters. A GaAs/AlGaAs DH layer was grown on the selectively etched hemispherical well for optical device application such as lensed surface emitting LED. The regrowth process were related with the coolin grate and the well to well spacing. A novel surface emitting LED with hemispherical AlGaAs lens was fabricated using the meltbakc and regrowth as the key process for AlaAs lens array. The light emitting efficiency of the LED was upto three times higher than the similar structure LED without lens. The meltback and regrowth technique was applicable to manufacture the optical device in LPE.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.83-85
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• 2004

MOCVD(metalorganic chemical vapor deposition)에 의해 성장된 InGaAs/AlGaAs 물질을 이용하여 V-형 양자선 (V-groove quantum-wire) 어레이(array) 구조에서 이득 결합(gain-coupling)에 의한 분포 광귀환(distributed optical feedback) 특성을 조사하였다. 분포 귀환형 (distributed feedback, DFB) 구조를 제작하는 동안 격자 재성장(grating overgrowth)을 피하기 위하여, 새롭게 개발된 constant MOCVD 성장 방법을 적용하였고, Bragg 파장에서 DFB 방향으로 광귀환의 결과인 스펙트럼의 이득 이방성(gain asymmetry)을 실험적으로 관찰하였다.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.118-122
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• 2003

Using low pressure metalorganic chemical vapor deposition (MOCVD), we have developed selectively area epitaxy (SAE). Using the developed SAE technology, we have grown AlGaAs/GaAs multi layers and InGaAs/GaAs quantum wire structures on the selectively $SiO_2$ masked GaAs substrates. We have obtained triangular shaped AlGaAs/GaAs and InGaAs/GaAs structures with sharp tips and smooth sidewalls. To rod the optimum conditions, several growth parameters such as growth rate, V/III ratio, growth temperature, and direction of the opening stripes were investigated. The emission peak from quantum wires was observed at 975 nm. With increasing of temperature the emission intensity from side wall quantum wells decreased abruptly. But the intensity from Quantum wires decreased slowly compared to that of side wall quantum wells and it became even stronger from above 50 K.

• Journal of the Korean Vacuum Society
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• v.2 no.1
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• pp.34-40
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• 1993

새로운 단결정 박막 성장방법으로 최근에 많은 관심을 끌고 있는 초고진공 화학기상증착법(Ultra-High Vacuum Chemical Vapor Deposition)을 이용하여 AlGaAs에 에피탁시 박막을 성장시켰다. AlGaAs 에피탁시층의 성장은 2。 경사진 GaAs(100) 기판을 사용하였다. 반응 기체로는 Trimethylgallium(TMGa), Trimethylaluminum(TMAl)과 arsine을 사용하였고, 성장온도는 $580~700^{\circ}C$, 기체 압력은 10-5~10-4Torr를 유지하였다. 특히 본 연구에서는 arsine을 사전에 열분해 하는 통상의 Chemical Beam Epitaxy(CBE) 성장법과는 달리, arsine이 표면에서 분해되는 화학 반응만을 사용하여도 AlGaAs 에피탁시를 성장할 수 있음은 물론 박막내의 탄소 불순물의 농도가 크게 낮아짐을 관찰하였다. 또한 성장 온도의 변화에 따른 AlGaAs 에피탁시층의 Al 함유 과정에 대하여도 고찰하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.414-414
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• 2013

InGaAlAs/InP은 $1.3{\sim}1.55{\mu}m$ 레이저 다이오드 응용을 위한 InGaAsP/InP를 대체하기 위한 물질로 많은 관심을 받아왔다. 디지털 합금 InGaAlAs 다중양자우물(multiple quantum wells: MQWs) 시료는 MBE (molecular beam epitaxy) 장비를 이용하여 n-InP 기판 위에 성장하였다. 양자우물과 장벽은 각각 (InGaAs)0.8(InAlAs)0.2와 (InGaAs)0.4(InAlAs)0.6 SPSs (short-period superlattices)로 $510^{\circ}C$에서 성장하였다. 발광특성을 향상시키기 위하여 질소분위기에서 $700^{\circ}C$ $750^{\circ}C$ 또는 $800^{\circ}C$에서 30초간 열처리(rapid thermal annealing: RTA)하였다. RTA 온도에 따른 디지털 합금 InGaAlAs MQWs의 발광특성을 분석하기 위해 PL (photoluminescence)과 TRPL(time-resolved PL)을 이용하였다. RTA 온도에 따른 InGaAlAs MQWs 시료의 발광 메카니즘 및 운반자 동력학을 연구하기 위하여 발광파장 및 온도에 따른 TRPL을 측정하였다. 저온(10 K)에서 PL 피크는 RTA 온도를 $700^{\circ}C$에서 $750^{\circ}C$로 증가하였을 때 1,242 nm에서 1,245 nm로 장파장 영역으로 이동하였다가 $800^{\circ}C$에서 열처리하였을 때 단파장 영역으로 이동하여 1,239 nm에서 나타났다. 또한 PL 세기는 RTA 온도를 증가함에 따라 증가함을 보이다가 RTA 온도를 $800^{\circ}C$로 증가하였을 때 PL 세기는 감소하였다. 발광소자 개발을 위한 InAlGaAs MQWs 시료의 최적의 열처리 조건을 이러한 PL과 TRPL 결과로부터 결정할 수 있다.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.308-314
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• 1999

We used the photoreflectance spectroscopy for characterization of the infrared photodetector structure we GaAs/$Al_{0.3}Ga_{0.7}As$ multi-quantum well (MQW) structures grown by molecular beam epitaxy (MBE) method. Energy gap related transitions in GaAS and AlGaAs were observed. The Al composition(x) was determined b Sek's composition formula. MQW related transition energies were identify the transitions, the experimentally observed energies were compare with results of the envelope function approximation for a rectangular quantum well.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.287-293
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• 1988

This paper calculates the band structure of the GaAs/(Al,Ga) As semiconductor superlttice with the interface3 grading, in consideration of different effective masses in each region. Including the effective masses, superlattice period, well and barrier widths, and the interface, the dispersion relation is derived, and the effects that the above parameters affect the subband (or miniband) structure of the superlattice and effective energy gap are investigated. It is particularly found that this case(ma<>mb<>mc) is significantly different from the same effective mass case(ma<>mb<>mc).

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.165-165
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• 2010

$1.55\;{\mu}m$ 대역의 레이저 다이오드를 제작하기 위해, InP(001) 기판에 InAlGaAs 물질을 장벽층으로 하는 InAs 양자점 구조를 분자선증착기 (MBE)를 이용하여 성장하고 구조 및 광학적 특성을 Double Crystal X-ray Diffraction (DCXRD), Atomic Force Microscopy (AFM), Photoluminescence (PL)을 이용하여 평가하였다. 일반적으로 InAlGaAs 물질은 고유한 상분리 현상 (Phase Separation)이 나타나는 특성이 있으며, 이는 양자점 성장에 중요한 요인으로 작용할 수 있다. 이러한 InAlGaAs 물질의 상분리 현상을 기판온도 ($540^{\circ}C$, $555^{\circ}C$, $570^{\circ}C$)를 비롯한 성장변수를 변화시켜 제어하고 InAs 양자점 형성에 어떠한 영향을 미치는지를 분석하였다. 540의 성장온도에서 InP(001) 기판에 격자정합한 InAlGaAs 장벽층이 성장온도를 $570^{\circ}C$로 증가시킬 경우 기판에 대하여 인장 응력 (Tensile Strain)을 받는 구조로 변화되었다. 인장응력을 받는 InAlGaAs 장벽층을 Ga Flux 양을 조절하여 격자정합한 InAlGaAs 층을 형성할 수 있었다. AFM을 통한 표면 형상 분석 결과, 서로 다른 기판온도에서 성장한 InAlGaAs 물질이 InP(001) 기판에 격자정합 조건일지라도 표면의 거칠기 (Surface Roughness)는 매우 다른 양상을 보였고 InAs 양자점 형성에 직접적으로 영향을 주었다. $570^{\circ}C$에서 성장한 InAlGaAs 위에 형성한 InAs 양자점의 가로방향 크기를 세로방향 크기로 나눈 비율이 1.03으로서, 555와 $540^{\circ}C$의 1.375 와 1.636와 비교할 때 모양 대칭성이 현저히 개선된 것을 알 수 있다. 상분리 현상이 줄어 표면 거칠기가 좋은 InAlGaAs 위에 양자점을 형성할 때 원자들의 이동도가 상대적으로 높아 InAs 양자점의 크기가 증가하고, 밀도가 감소하는 현상이 나타났다. 또한 InAlGaAs 장벽층이 InP(001) 기판을 기준으로 응력 (Compressive 또는 Tensile)이 존재하는 경우, InAs 양자점 모양이 격자정합 조건 보다 비대칭적으로 변하는 특성을 보여 주었다. 이로부터, 대칭성이 개선된 InAs 양자점 형성에 InAlGaAs 장벽층의 표면 거칠기와 응력이 중요한 변수로 작용함을 확인 할 수 있었다. PL 측정 결과, 발광파장은 $1.61\;{\mu}m$로 InAs 양자구조 형상에 따라 광강도 (Intensity), 반치폭 (Line-width broadening) 등이 변화 되었다.

• 전기의세계
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• v.28 no.4
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• pp.53-63
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• 1979

Interface recombination velocity in $Al_{x}$G $a_{1-x}$ As-GaAs and $Al_{0.85}$, G $a_{0.15}$ As-GaA $s_{1-y}$S $b_{y}$ heterojunction systems is studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n $Al_{x}$G $a_{1-x}$ As-GaA $s_{1-y}$S $b_{y}$-A $l_{x}$G $a_{1-x}$ As double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAs Sb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates. In the AlGaAs system, elastic lattice deformation with effective Poisson ratios .mu.$_{eff}$ (100=0.312 and .mu.$_{eff}$ (111B) =0.190 was observed. The lattice constant $a_{0}$ (A $l_{x}$G $a_{1-x}$ As)=5.6532+0.0084x.angs. was obtained at 300K which is in good Agreement with Vegard's law. In the GaAsSb system, although elastic lattice deformation was observed in (111) B-oriented crystals, misfit dislocations reduced the Poisson ratio to zero in (100)-oriented samples. When $a_{0}$ (GaSb)=6.0959 .angs. was assumed at 300K, both (100) and (111)B oriented GaAsSb layers deviated only slightly from Vegard's law. Both (100) and (111)B zero-mismatch $Al_{0.85}$ G $a_{0.15}$As-GaA $s_{1-y}$S $b_{y}$ layers were grown from melts with a weight ratio of $W_{sb}$ / $W_{Ga}$ =0.13 and a growth temperature of 840 to 820 .deg.C. The corresponding Sb compositions were y=0.015 and 0.024 on (100) and (111)B orientations, respectively. This occurs because of a fortuitous in the Sb distribution coefficient with orientation. Interface recombination velocity was estimated from the dependence of the effective minority carrier lifetime on double-heterojunction spacing, using either optical phase-shift or electroluminescence timedecay techniques. The recombination velocity at a (100) interface was reduced from (2 to 3)*10$^{4}$ for y=0 to (6 to 7)*10$^{3}$ cm/sec for lattice-matched $Al_{0.85}$G $a_{0.15}$As-GaA $s_{0.985}$S $b_{0.015}$ Although this reduction is slightly less than that expected from the exponential relationship between interface recombination velocity and lattice mismatch as found in the AlGaAs-GaAs system, solar cells constructed from such a combination of materials should have an excellent spectral response to photons with energies over the full range from 1.4 to 2.6 eV. Similar measurements on a (111) B oriented lattice-matched heterojunction produced some-what larger interface recombination velocities.ities.ities.s.