• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.235-238
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• 1996

An inverted double channel AIGaAs/lnGaAs/GaAs heterostructure grown by LP-MOCVD is demonstrated and discussed. Sheet carrier densities in excess of $4.5{\times}10^{12}cm^{-2}$ at 300K are obtained with a hall mobility of $5010cm^2/V{\cdot}s$. The proposed device with a $1.8{\times}200{\mu}m^2$ gate dimension reveals an extrinsic transconductance as high as 320 mS/mm and a saturation current density as high as 820 mA/mm at 300K. This is the highest current density ever reported for GaAs MODFET's with the same gate length. Significantly improvements on gate voltage swing (up to 3.5 V) and on reverse breakdown voltage (-10V) are demonstrated due to inverted structure.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.135-140
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• 2011

By investigating photoluminescence (PL) spectra (20 K) of undoped and Be-doped p-type GaSb/GaAs epilayers, the origin has been analyzed by the change due to doping density. We have observed that the PL peak shifts to higher energy and the full-width half-maximum (FWHM) decreases with increasing the doping density below ${\sim}10^{17}cm^{-3}$, contrasted to shift to low energy and increasing FWHM above the density of ${\sim}10^{17}cm^{-3}$. From the variation of the integrated PL intensities of three peaks dissolved by Gaussian fit, it has been analyzed that, as the density increases, the $Be[Be_{Ga}]$ acceptor level (0.794 eV) reduces, whereas the intrinsic defect of $A[Ga_{Sb}]$ (0.778 eV) enhances together with a new $Be^*$ level (0.787 eV) locating between A and Be. We have discussed that it is due to coexistence of the Be acceptor level (${\Delta}E=16meV$) and the complex level (${\Delta}E=23meV$), $Be^*[Ga_{Sb}-Be_{Ga}]$combined by Be and A, in Be-doped p-GaSb, and that the level density of $Be[Be_{Ga}]$ may be reduced above ${\sim}10^{17}cm^{-3}$.

• Proceedings of the Botanical Society of Korea Conference
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• 1987.07a
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• pp.133-148
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• 1987

Gibberellin(GA) 3-$\beta$ hydroxylation is very important for the shoot elogation in the higher plants, since only 3$\beta$-hydryoxylated GAs promote shoot elogation in several plants. Fluctuation of 3$\beta$-hydryoxylase activity was examined during seed maturation using two cultivars of , P. vulgaris, Kentucky Wonder (normal) and Masterpiece (dwarf). Very immature seeds of both cultivars contain high level of 3$\beta$-hydroxylase activity (per mg protein). Both cultivars showed maximum of enzyme activity (per seed) in the middle of their maturation process. Gibberellin 3$\beta$-hydroxylase catalyzing the hydroxylation of GA20 to GA1 was purified 313-fold from very early immature seeds of P. vulgaris. Crude soluble enzyme extracts were purified by 15% methanol precipitation, hydrophobic interaction chromatogrphy, DEAE ion exchange column chromatography and gel filtration HPLC. The 3$\beta$-hydroxylase activity was unstable and lost much of its activity duting the purification. The molecular weight of purified enzyme was extimated to be 42, 000 by gel filtration HPLC and SDS-PAGE. The enzyme exhibited maximum activity at pH 7.7. The Km values for [2.3-3H] GA20 and [2.3-3H]GA9 were 0.29 $\mu$M and 0.33 $\mu$M, respectively. The enzyme requires 2-oxoglutarate as a cosubstrate; the Km value for 2-oxoglutarate was 250 $\mu$M using 3H GA20 as a substrate. Fe2+ and ascorbate significantly activated the enzyme at all purification steps, while catalase and BSA activated the purified enzyme only. The enzyme was inhibited by divalent cations Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+. Effects of several GAs and GA anaogues on the putrified 3$\beta$-hydroxylase were examined using [3H]GA9 and GA20 as a substrates. Among them, GA5, GA9, GA15, GA20 and GA44 inhibited the enzyme activity. [13C, 3H] GA20 was converted by the partially purified enzyme preparation to [13C, 3H]GA1, GA5 and GA6, which were identified by GC-MS, GA9 was converted only GA4, GA15 and GA44 were converted to GA37 and GA38, respectively. GA5 was epoxidized to GA6 by the preparation. This suggests that 3$\beta$-hydroxylation of GA20 and epoxidation of GA5 are catalyzed by the same enzyme in P, vulgaris.

• Journal of electromagnetic engineering and science
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• v.4 no.4
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• pp.156-161
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• 2004

The MMIC cascode VCO is designed, fabricated, and measured for Ku-band Low Noise Blcok(LNB) system using InGaP/GaAs HBT technology. The phase noise of -116.4 dBc/Hz at 1 MHz offset with output power of 1.3 dBm is obtained at 11.526 GHz by applying 3 V and 11 mA, which is comparatively better characteristics than compared with the different configuration VCOs fabricated with other technologies. The simulated results of oscillation frequency and second harmonic suppression agree with the measured results. The phase noise is improved due to the use of the smallest value of inductor in frequency determining network and the InGaP ledge function of the technology. The chip size of $830\time781\;{\mu}m^2$ is also achieved.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.368-371
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• 1988

The MS diodes made by evarporating In, Au/Ge on the p-GaP substrates, and the p-n diode made by diffusing Te in the p-GaP were fabricated, and its electric-optical characteristics were surveyed. The maximum peak of E.L spectrum was shifted towards the longer wavelengths with increasing temperature, and its intensity increased with in-creasing of current. The MS diodes were fabricated rather easily and is electric-optical characteristics was as good as that of p-n diodes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.93-97
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• 1990

Interfacil charge approximations and structures at doped semiconductor interfaces were proposed. Rectifying phenomena at the III-V compound semiconductor (p-GaP, p-InP, n-GaAs)/$CsNO_3$ aqueous electrolyte interfaces were qualitatively analyzed in terms of their cyclic current-voltage characteristics. The current-voltage characteristic curves, the ion adsorption and potential barrier processes at the semiconductor interfaces were verified using continuous cyclic voltammetric methods. The pn or np junction structures and the related rectifying types at the doped semi-condudtor-electrolyte inferfaces are determined by the space charges.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.902-911
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• 2003

Using InGaP/GaAs HBT power cells with a 2.0${\times}$20$\mu\textrm{m}$$^2$ emitter area of a unit HBT, a two stage MMIC power amplifier has been developed for IMT-2000 handsets. An active-bias circuit has been used for temperature compensation and reduction in the idling current. Fitting on measured S-parameters of the HBT cells, circuit elements of HBT's nonlinear equivalent model have been extracted. The matching circuits have been designed basically with the extracted model. A two stage HBT MMIC power amplifier fabricated using ETRI's HBT process. The power amplifier produces an 1-㏈ compressed output power(P$\_$l-㏈/) of 28.4 ㏈m with 31% power added efficiency(PAE) and 23-㏈ power gain at 1.95 GHz in on-wafer measurement. Also, the power amplifier produces a 26 ㏈m output power, 28% PAE and a 22.3-㏈ power gain with a -40 ㏈c ACPR at a 3.84 ㎒ off-center frequency in COB measurement.quency in COB measurement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.433-434
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• 2008

반도체 공정 기술의 진보로 인해 InP/InGaAs로 제작된 애벌랜치 포토다이오드가 고속 광통신 시스템에서 사용되고 있다. 하지만 경계 항복에 의한 접합 부분의 강한 전기장으로 인한 문제와 항복 이득의 저하 문제로 소자 특성의 문제가 발생하고 있다. 이 논문에서는 소자 구조 변화에 따른 고속 InP/InGaAs 애벌랜치 포토다이오드의 특성 변화를 공정/소자 시뮬레이션을 이용하여 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.168-168
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• 2010

InAs는 0.35eV의 낮은 밴드갭을 가지며 상온에서 약 $30,000cm^2/Vs$의 높은 전자이동도를 보여, GaAs/AlGaAs 및 InGaAs/InP 2DEG HEMT에 이은 차세대 초고속 전자소자의 2DEG용 물질로 각광을 받고 있다. 그러나 InAs의 격자상수는 약 0.61nm로 이에 적절한 반절연기판을 구할수 없어, GaAs상에 Al(Ga)Sb를 이용하여 성장하는 방법으로 2DEG을 실현하고 있다. 상기 방법으로 상온에서 ${\sim}30,000cm^2/Vs$ 전자이동도를 보이는 InAs/AlSb 2DEG HEMT 소자를 여러 연구팀에서 시현하였으나, 실제적으로 응용하기 위해서 etch-stop층 또는 contact층의 제작이 용이치 않아 실제의 회로구현에는 어려움을 격고 있다. 이에 InGaAs/InP 2DEG내에 InAs를 넣어 InAs 2DEG을 제작하는 방법이 NTT[1]에 의해 제안되어, SPINTRONICS등의 InAs 2DEG이 필요한 곳에 응용되고 있다. [2] 본 발표에서는 고품질의 InAs 2DEG을 실현하기 위해, 다양한 성장 변수 (온도, As 분압, 성장 시퀀스, InAs층의 두께등)와 2DEG의 전기적특성간의 관계를 발표한다. 최종적으로 상온전자이동도 ${\sim}12,000cm^2/Vs$의 InAs 2DEG을 제작할수 있었으며, 이를 다양한 전자소자에 차후 응용할 예정이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.143-144
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• 2010

3-5족 화합물 반도체를 이용한 집광형 삼중 접합 태양전지는 40% 이상의 광변환 효율로 많은 주목을 받고 있다[1]. 삼중 접합 태양전지의 하부 셀은 기계적 강도가 높고 장파장을 흡수할 수 있는 Ge이 사용된다. Ge위에 성장될 III-V족 단결정막으로서 Ge과 격자상수가 일치하는 GaInP나 GaAs가 적합하고, 성장 중 V족 원소의 열확산으로 인해 Ge과 pn접합을 형성하게 된다. 이때 GaInP의 P의 경우 GaAs의 As보다 확산계수가 낮아 태양전지 변환효율향상에 유리한 얇은 접합 형성이 가능하고, 표면 에칭효과가 적기 때문에 GaInP를 단결정막으로 선택하여 p-type Ge기판 위 성장으로 단일접합 Ge구조 제작이 가능하다. 하지만 이종접합 구조 성장으로 인해 발생한 계면사이의 전위나 미세결함들이 결정막내부에 존재하게 되며 이러한 결함들은 광학소자 응용 시 비발광 센터로 작용할 뿐 아니라 소자의 누설전류를 증가시키는 원인으로 작용하여 태양전지 변환효율을 감소시키게 된다. 이에 결함감소를 통해 소자의 전기적 특성을 향상시키고자 수소 열처리나 플라즈마 공정을 통해 수소 원자를 박막내부로 확산시키고, 계면이나 박막 내 결함들과 결합시킴으로서 결함들의 비활성화를 유도하는 연구가 많이 진행되어 왔다 [2][3]. 하지만, 격자불일치를 갖는 GaInP/Ge 구조에 대한 수소 열처리 및 불순물 준위의 거동에 대한 연구는 많이 진행되어 있지 않다. 따라서 본 연구에서는 Ga0.45In0.55P/Ge구조에 수소 열처리 공정을 적용을 통하여 단결정막 내부 및 계면에서의 결함밀도를 제어하고 이를 통해 태양 전지의 변환효율을 향상시키고자 한다. <111> 방향으로 $6^{\circ}C$기울어진 p-type Ge(100) 기판 위에 유기금속화학증착법 (MOCVD)을 통해 Si이 도핑된 200 nm의 n-type GaInP층을 성장하여 Ge과 단일접합 n-p 구조를 제작하였다. 제작된 GaInP/Ge구조를 furnace에서 250도에서 90~150분간 시간변화를 주어 수소열처리 공정을 진행하였다. 저온 photoluminescence를 통해 GaInP층의 광학적 특성 변화를 관찰한 결과, 1.872 eV에서 free-exciton peak과 1.761 eV에서 Si 도펀트 saturation에 의해 발생된 D-A (Donor to Acceptor)천이로 판단되는 peak을 검출할 수 있었다. 수소 열처리 시간이 증가함에 따라 free-exciton peak 세기 증가와 반가폭 감소를 확인하였고, D-A peak이 사라지는 것을 관찰할 수 있었다. 이러한 결과는 수소 열처리에 따른 단결정막 내부의 수소원자들이 얕은 불순물(shallow impurity) 들로 작용하는 도펀트들이나, 깊은 준위결함(deep level defect)으로 작용하는 계면근처의 전위, 미세결함들과의 결합으로 결함 비활성화를 야기해 발광세기와 결정질 향상효과를 보인 것으로 판단된다. 본 발표에서는 상술한 결과를 바탕으로 한 수소 열처리를 통한 박막 및 계면에서의 결함준위의 거동에 대한 광분석 결과가 논의될 것이다.