• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
• /
• pp.1-7
• /
• 1997

The goals of the present study lie in presenting the direction of researches and developments for GaAs based solar cells, as well as in taking a step toward the establishment of GaAs MOCVD technologies. On the other hand, the GaAs on Si substrates has been recognized as a lightweight alternative to pure GaAs substrate for space application, because its density is less than the 7alf of GaAs or Ge. So, GaAs/Si has twofold weight advantage to GaAs monolithic cell. It was concluded that the development the development of MOCVD technologies should be ahead of GaAs solar cells.

• Journal of Ceramic Processing Research
• /
• 제19권5호
• /
• pp.439-443
• /
• 2018

The outstanding characteristics of high quality GaN single crystal substrates make it possible to apply the manufacture of high brightness light emitting diodes and power devices. However, it is very difficult to obtain high quality GaN substrate because the process conditions are hard to control. In order to effectively control the formation of GaN polycrystals during the bulk GaN single crystal growth by the HVPE (hydride vapor phase epitaxy) method, a quartz ring was introduced in the edge of substrate. A variety of evaluating method such as high resolution X-ray diffraction, Raman spectroscopy and photoluminescence was used in order to measure the effectiveness of the quartz ring. A secondary ion mass spectroscopy was also used for evaluating the variations of impurity concentration in the resulting GaN single crystal. Through the detailed investigations, we could confirm that the introduction of a quartz ring during the GaN single crystal growth process using HVPE is a very effective strategy to obtain a high quality GaN single crystal.

• 센서학회지
• /
• 제23권1호
• /
• pp.51-57
• /
• 2014

The evaporating materials for $MgGa_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MgGa_2Se_4$ compounded polycrystal powder was deposited on thoroughly etched semi-insulated GaAs(100) substrate by the hot wall epitaxy (HWE) method system. The source and substrate temperatures of optimized growth conditions, were $610^{\circ}C$ and $400^{\circ}C$, respectively.The source and substrate temperatures were $610^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MgGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.34\;eV-(8.81{\times}10^{-4}\;eV/K)T^2/(T+251\;K)$. After the as-grown $MgGa_2Se_4$ single crystal thin films was annealed in Mg-, Se-, and Ga-atmospheres, the origin of point defects of $MgGa_2Se_4$ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Mg}$, $V_{Se}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted $MgGa_2Se_4$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $MgGa_2Se_4$/GaAs did not form the native defects because Ga in $MgGa_2Se_4$ single crystal thin films existed in the form of stable bonds.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.65-66
• /
• 2009

This paper describes a procedure developed to fabricate negative photo resist SUMS to a semi-insulating (SI)-GaAs-based substrate. SU-8 is attractive for micromachine multi-layer circuit fabrication, because it is photo-polymerizable resin, leading to safe, and economical processing. This work demonstrates SUMS photo resist can be used for RFIC/MMIC application.

• 한국진공학회지
• /
• 제17권3호
• /
• pp.211-214
• /
• 2008

Metal organic chemical vapor deposition (MOCVD)를 이용하여 사파이어 기판 위에 405 nm의 파장을 갖는 GaN light-emitting diode (LED)를 제작하였다. LED의 InGaN 활성층에서 생성되어 칩의 후면으로 향하는 광자를 전면으로 반사시키기 위하여, 사파이어 기판 후면에 반사막을 증착하였다. 반사막으로는 Al을 사용하였으며, 사파이어 기판에 대한 Al 박막의 접착력을 개선하기 위하여 사파이어 기판 후면에 Ti를 먼저 증착한 후에 Al을 증착하였다. Ti-Al 반사막을 채용한 결과, 광추출 효율이 52 % 향상되었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
• /
• pp.124-127
• /
• 2003

The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnance. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at $630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is $2.1{\mu}m$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. From the photoluminescence measurement of $AgGaSe_2$ single crystal thin film, we observed free excition ($E_x$) observable only in high quality crystal and neutral bound excition ($D^{\circ}$,X) having very strong peak intensity. And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 14.1 meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.

• 마이크로전자및패키징학회지
• /
• 제16권4호
• /
• pp.29-32
• /
• 2009

기공의 밀도가 높은 다공성 실리콘 산화물 박막이 GaAs 기판 상에 형성이 되었다. 다공성 실리콘 산화막을 형성하기 위해서 자기조립 형태로 배열하는 블록공중합체를 사용하였다. GaAs 기판 상에 화학기상증착 (CVD)을 이용하여 실리콘 산화막을 형성하였다. 폴리스티렌 (PS) 바탕에 벌집 형태로 배열된 폴리메틸메타아크릴레이트 (PMMA)가 주기적으로 배열되어 있는 나노패턴 박막을 형성하였고 PMMA를 아세트 산으로 제거하여 PS만 남아있는 나노크기의 마스크를 형성하였다. 형성된 PS 나노패턴의 지름은 15 nm, 박막의 두께는 40 nm 였으며 이를 건식 식각용 마스크로 사용하여 화학반응성식각 (RIE) 을 진행하였고 PS의 나노패턴이 산화막 기판상에 전사되도록 하였다. 식각 시간을 조절하여 산화막에 형성된 기공이 GaAs 표면까지 연결되도록 하였고 이는 불산으로 산화막을 제거하여 확인하였다. 식각시간은 90초에서 110초였으며 산화막 상에 나노패터닝된 기공이 형성되는 식각 시간은 90초에서 100초 사이였다. 형성된 나노 패터닝된 산화막 기공의 지름은 20~22 nm였고 식각 시간에 따라서 조절이 가능함을 확인할 수 있었다.

• 한국에너지공학회:학술대회논문집
• /
• 한국태양에너지학회, 한국에너지공학회 1993년도 춘계 공동학술발표회 초록집
• /
• pp.53-59
• /
• 1993

The interests on GaAs solar cell grown on Ge substrates as an alternative of GaAs substrate arises from its very close lattice parameters, very small difference in thermal expansion coefficients, and much higher fracture toughness between GaAs and Ge. In addition, for many space power application, it would be a most attractive solar cell with high radiation resistance of GaAs and high reliability for the reverse current damage of Ge, and expecting the theoretical efficiency limit of the tandem GaAs/Ge solar cell is 34% under 1 Sun, AM 0, and 28$^{\circ}C$ condition. In this report, we have reviewed the performance and the manufacturing technics of GaAs/Ge solar cell, and current status of research in GaAs/Ge solar cell.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.420-420
• /
• 2013

We investigated oxygen plasma effect on defect states near the interface of AlGaN/GaN High Electron Mobility Transistor (HEMT) structure grown on a silicon substrate. After the plasma treatment, electrical properties were evaluated using a frequency dependant Capacitance-Voltage (C-V) and a temperature dependant C-V measurements, and a deep level transient spectroscopy (DLTS) method to study the change of defect densities. In the depth profile resulted from the temperature dependant C-V, a sudden decrease in the carrier concentration for two-dimensional electron gas (2DEG) nearby 250 K was observed. In C-V measurement, the interface states were improved in case of the oxygen-plasma treated samples, whereas the interface was degraded in case of the nitrogen-plasma treated sample. In the DLTS measurement, it was observed the two kinds of defects well known in AlGaN/GaN structure grown on sapphire substrate, which have the activation energies of 0.15 eV, 0.25 eV below the conduction band. We speculate that this defect state in AlGaN/GaN on the silicon substrate is caused from the decrease in 2DEG's carrier concentrations. We compared the various DLTS signals with filling pulse times to identify the characteristics of the newly found defect. In the filling pulse time range under the 80 us, the activation energies changed as the potential barrier model. On the other hand, in the filling pulse time range above the 80 us, the activation energies changed as the extended potential model. Therefore, we suggest that the found defect in the AlGaN/GaN/Si structure could be the extended defect related with AlGa/N/GaN interface states.

• 한국진공학회지
• /
• 제7권s1호
• /
• pp.15-19
• /
• 1998

Structural and optical properties of $In_xGa_{1-X}N$ as well as $In_{0.1}Ga_{0.9}N$/GaN single quantum we11 (SQW) grown on sapphire (0001) substrate with an based GaN using rf-plasma assisted MBE have been investigated. The quality of the InXGal.,N fdm was improved as the growth temperature increased. In PL measurements at low temperatures, the band edge emission peaks of $In_xGa_{1-X}N$ was shifted to red region as an indium cell and substrate temperature increased. For $In_{0.1}Ga_{0.9}N$/GaN SQW, the optical emission energy has blue shift about 15meV in PL peak, due to the confined energy level in the well region. And, the FWHM of the $In_{0.1}Ga_{0.9}N$/GaN SQW was larger than that of the bulk Ino,la.9N films. The broadening of FWHM can be explained either as non-uniformity of Indium composition or the potential fluctuation in the well region. Photoconductivity (PC) decay measurement reveals that the optical transition lifetimes of the SQW measured gradually increased with temperatures.