• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.504-508
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• 2019

The feasibility of replacing the tope cell of pn GaInP homojunction with our GaInP/AlGaInP heterojunction structure in III-V semiconductor multijunction photovoltaic (MJPV) cells having the highest current conversion efficiency was investigated. The performance of photovoltaic (PV) cells grown on $2^{\circ}$ and $10^{\circ}$ off-oriented GaAs substrates were compared to each other. The PV cells on the $10^{\circ}$ off-cut substrate showed higher short-circuit current density ($J_{sc}$) and conversion efficiency values than that of using the $2^{\circ}$ one. For $2{\times}2mm^2$ area PV cell on $10^{\circ}$ off substrate, the $J_{sc}$ of $9.21mA/cm^2$ and the open-circuit voltage of 1.38 V were measured under 1 sun illumination. For $5{\times}5mm^2$ cell on $10^{\circ}$ off substrate, the conversion efficiency was decreased from 6.03% (1 sun) to 5.28% (20 sun) due to a decrease in fiill factor (FF).

• Korean Journal of Materials Research
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• v.18 no.8
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• pp.444-449
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• 2008

Samples of GaMnAs, GaMnAs codoped with Be, and GaMnAs simultaneously codoped with Be and Mg were grown via low-temperature molecular beam epitaxy (LT-MBE). Be codoping is shown to take the Ga sites into the lattice efficiently and to increase the conductivity of GaMnAs. Additionally, it shifts the semiconducting behavior of GaMnAs to metallic while the Mn concentration in the GaMnAs solid solution is reduced. However, with simultaneous codoping of GaMnAs with Be and Mg, the Mn concentration increases dramatically several times over that in a GaMnAs sample alone. Mg and Be are shown to eject Mn from the Ga sites to form MnAs and MnGa precipitates.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.166-166
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• 2010

산업 전반에 걸쳐 중요한 광원인 808 nm 대역의 레이저 다이오드 제작에는 현재 InGaAsP/InGaP/GaAs 및 InGaAlAs/GaAs 양자우물을 이용하여 제작되고 있다. 이는 양자우물과 이를 둘러싸는 장벽물질간의 band-offset이 적어 효율적인 고출력 레이저 다이오드의 제작에 어려움이 있기 때문에 강한 캐리어 구속 효과를 지니는 양자점을 사용하는 것이 고출력 레이저 다이오드를 제작할 수 있는 방법이다. 실험에 사용된 InAlAs 양자점은 Riber사의 compact21 MBE 장치를 사용하여 성장하였으며 GaAs기판을 610도에서 가열하여 표면의 산화층을 제거하고 580도에서 약 100 nm 두께의 GaAs 버퍼층 및 30 nm 두께의 $Al_{0.4}Ga_{0.6}As$층을 성장하였다. GaAs 기판의 온도를 내린 후 migration enhanced epitaxy 방법을 사용하여 InAs 및 AlAs를 번갈아 주입하여 성장하였다. InAlAs 양자점의 성장 중에 InAlAs의 양, 성장 온도, As flux량 및 As 분자 상태 변화 등 다양한 조건을 변화 시켜 샘플을 성장시켰다. 그 결과 기판 온도가 600도이며 As4 flux가 $1\;{\times}\;10^{-6}\;Torr$ 조건하에서 성장한 InAlAs/AlGaAs 양자점이 양질의 808 nm의 파장 대역을 얻을 수 있었다.

• 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.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.2
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• pp.63-68
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• 2003

The DC and RF characteristics of $In_{0.5}Ga_{0.5}P/In_{0.22}Ga_{0.78}As/GaAs$ p-HEMTs with a gate oxide layer of various thicknesses ($50{\;}{\AA},{\;}300{\;}{\AA}$) were investigated and compared with those of a Schottky-gate p-HEMT without the gate oxide layer. A prominent improvement in the breakdown voltage characteristics were observed for a p-HEMT having a gate oxide layer, which was implemented by using a liquid phase oxidation technique. The on-state breakdown voltage of the p-HEMT having the oxide layer of $50{\;}{\AA}$was ~2.3 times greater than that of a Schottky-gate p-HEMT. However, the p-HEMT having the gate oxide layer of $300{\;}{\AA}$ suffered from a poor gate-control capability due to the drain induced barrier lowering (DIBL) resulting from the thick gate oxide inspite of the lower gate leakage current and the higher on-state breakdown voltage. The results for a primitive p-HEMT having the gate oxide layer without any optimization of the structure and the process indicate the potential of p-HEMT having the gate oxide layer for high-power applications.

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.98-98
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• 1996

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.68-72
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• 2004

The integrated voltage-controlled-oscillator(VOC) operating at 1.75 ㎓ is designed using the InGaP/GaAs HBT process. The proposed noise removal circuit and FR-4 substrate structure in this letter show the better characteristic of the phase noise and reduce the size of the VCO. The frequency tuning range of the VCO is about 200 ㎒ and the phase noise at 120 ㎑ offset is -119.3 ㏈c/㎐. The power consumption of the VCO core is 11.2 ㎽ at 2.8 V supply voltage and the output power is -2 ㏈m. The calculated figure of merit(FOM) is 191.7, which shows the best performance compared with the previous FET or HBT VCO.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.353-358
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• 2008

In order to increase extraction efficiency of AlGaInP-based vertical RED LEDs, chemical wet etching technique was produced by using a roughened surface with triangle-like morphology. A commonly used $H_3PO_4$-based solution was applied for chemical wet etching. The light extraction of AlGaInP LED was related to the n-side roughed surface morphology. The morphology of roughed surface is analyzed by the atomic force microscope (AFM). As a result, the roughed surface AlGaInP LED has a root-mean-square (RMS) roughness of 44 nm. The brightness shows 41% increase after roughening n-side surface, as compared to the ordinary flat surface LED.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.213-216
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• 2001

The use of a thin film of indium between the ITO and the $n^{+}$-InP contact layers for InP/InGaAs HPTs was studied without degrading its excellent optical transmittance properties. ITO/$n^{+}$-InP ohmic contact was successfully achieved by the deposition of Indium and thermal annealing. The specific contact resistance of about 6.6$\times$$10^{-4}$$\Omega\textrm{cm}^2$ was measured by use of the transmission line method (TLM). However, as the thermal annealing was just performed to ITO/$n^{+}$-InP contact without the deposition of Indium between ITO and $n^{+}$-InP, it exhibited schottky characteristics. In the applications, the DC characteristics of InP/InGaAs HPTs with ITO emitter contacts was compared with that of InP/InGaAs HBTs with the opaque emitter contacts.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1262-1268
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• 1995

Photoelectrochemical properties of p-GaAs electrode have been investigated. I-V characteristic shows that the cathodic photocurrent is observed at -0.7 V vs. SCE. The photoresponse at near 870~880nm wavelength indicates that the photogenerated carriers contibuted to the observed current. The maximum converson efficiency of 35% is obtained for a Xe lamp light source at 400nm. In C-V relation, capacitance peaks appeared at the frequencies of 100Hz and 300Hz due to the activation of the interfacial states which exist at the energy level corresponding to the one-third of the GaAs band gap. The difference of about 1.1V between flatband potential (Vfb) from the Mott-Schottky method and onset voltage from I-V curve is observed due to the trap of carriers at the interfacial states in the boundary between GaAs and electrolyte. In case of WO3 deposited p-GaAs electrode, higher positive onset current and photocurent density are obtained. This can be explained by the fact that carriers are generated by light penetrated into the WO3 thin flm as well as p-GaAs substrate and then move into the electrolyte effectively.