• 한국재료학회지
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• 제12권4호
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• 대한전자공학회논문지
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• 제26권11호
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• pp.1672-1678
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• 1989

Major problems preventing the device-quality GaAs/Si heterostructure are the lattice mismatch of about 4% and difference in thermal expansion coefficient by a factor of 2.64 between Si and GaAs. Ge is a good candidate for the buffer layer because its lattice parameter and thermal expansion coefficient are almost the same as those of GaAs. As a first step toward developing heterostructure such as GaAs/Ge/Si entirely by a home-built PAE (plasma-assisted epitaxy), Ge films have been deposited on p-type Si (100)substrate by the plasma assisted evaporation of solid Ge source. The characteristics of these Ge/Si heterostructure were determined by X-ray diffraction, SEM and Auge electron spectroscope. PAE system has been successfully applied to quality-good Ge layer on Si substrate at relatively low temperature. Furthermore, this system can remove the native oxide(SiO2) on Si substrate with in-situ cleaning procedure. Ge layer grown on Si substrate by PAE at substrate temperature of 450\ulcorner in hydrogen partial pressure of 10mTorr was expected with a good buffer layer for GaAs/Ge/Si heterostructure.

• 한국재료학회지
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• 제22권9호
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• pp.450-453
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• 2012

In crystalline solar cells, the substrate itself constitutes a large portion of the fabrication cost as it is derived from semiconductor ingots grown in costly high temperature processes. Thinner wafer substrates allow some cost saving as more wafers can be sliced from a given ingot, although technological limitations in slicing or sawing of wafers off an ingot, as well as the physical strength of the sliced wafers, put a lower limit on the substrate thickness. Complementary to these economical and techno-physical points of view, a device operation point of view of the substrate thickness would be useful. With this in mind, BC-BJ Si and GaAs solar cells are compared one to one by means of the Medici device simulation, with a particular emphasis on the substrate thickness. Under ideal conditions of 0.6 ${\mu}m$ photons entering the 10 ${\mu}m$-wide BC-BJ solar cells at the normal incident angle (${\theta}=90^{\circ}$), GaAs is about 2.3 times more efficient than Si in terms of peak cell power output: 42.3 $mW{\cdot}cm^{-2}$ vs. 18.2 $mW{\cdot}cm^{-2}$. This strong performance of GaAs, though only under ideal conditions, gives a strong indication that this material could stand competitively against Si, despite its known high material and process costs. Within the limitation of the minority carrier recombination lifetime value of $5{\times}10^{-5}$ sec used in the device simulation, the solar cell power is known to be only weakly dependent on the substrate thickness, particularly under about 100 ${\mu}m$, for both Si and GaAs. Though the optimum substrate thickness is about 100 ${\mu}m$ or less, the reduction in the power output is less than 10% from the peak values even when the substrate thickness is increased to 190 ${\mu}m$. Thus, for crystalline Si and GaAs with a relatively long recombination lifetime, extra efforts to be spent on thinning the substrate should be weighed against the expected actual gain in the solar cell output power.

• 한국결정성장학회지
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• 제1권1호
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• pp.82-91
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• 1991

분자선속 방법으로 실리콘 기판위에 GaAs의 에피층을 생장하고, 이를 분석한 결과를 보고한다. 두 종류의 실리콘 기판에 생장 조건을 다르게 한 시료를 준비하고, SEM, TEM, X-ray회절, PL, Hall 등의 방법으로 분석하였다. 결정면에서 약간 기울여 절삭한 기판에 이단계 성장법으로 성장한 에피층이 보다 좋은 결정 구조를 갖으며, multi-quantum well buffer layer를 삽입하는 것이 stress 해소 등에 도움이 된다. 또 GaAs 에피층은 저절로 실리콘으로 doping이 되는데, exciton bound 에너지 준위를 통한 radiative recombination은 homoepitaxial GaAs 에피층보다 잘 일어나지 않는 것으로 관측되었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.170-170
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• 2003

We have implanted on sapphire substrate with various ions and investigated the properties of GaN epilayers grown on implanted sapphire substrate by metal organic chemical vapor deposition (MOCVD). Sapphire is typical substrate for GaN epilayers. However, there are many problems such as lattice mismatch and thermal coefficient difference between sapphire substrate and GaN. The ion implanted substrate's surface had decreased internal tree energies during the growth of the GaN epilayer, md the misfit strain was relieved through the formation of an AlN phase on the ions implanted sapphire(0001) substrates. [1] The crystal and optical properties of GaN epilayer grown in ions implanted sapphire(0001) substrate were improved.

• 대한전자공학회논문지
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• 제23권2호
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• pp.243-248
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• 1986

The impurities in As and Ga sources and the contamination of the GaAs substrate prior to growing of MBE GaAs epitaxial layer have been investigated using RHEED, AES and RGA methods. The as source was contaminated by H2O, CO, CO2 and AsO, and the Ga source was contaminated by H2, H2O, CO and CO2. These contaminants could easily be removed by prebaking the source. On the other hand, GaAs substrate was contaminated principally carbon and oxygen. The oxygen could easily be removed by heating the substrate above 480\ulcorner, and the carbon could also be reduced by sputtering the substrate with 1ke V Ar+. The chemically etched substrate surface prior to growing the layer was rough, but it was made to be smooth and clean by heating it above 530 \ulcorner.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.51-51
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• 2010

Group III-nitride semiconductors have been widely studied as the materials for growth of light emitting devices. Currently, GaN devices are predominantly grown in the (0001) c-plane orientation. However, in case of using polar substrate, an important physical problem of nitride semiconductors with the wurtzite crystal structure is their spontaneous electrical polarization. An alternative method of reducing polarization effects is to grow on non-polar planes or semi-polar planes. However, non-polar and semipolar GaN grown onto r-plane and m-plane sapphire, respectively, basically have numerous defects density compared with c-plane GaN. The purpose of our work is to reduce these defects in non-polar and semi-polar GaN and to fabricate high efficiency LED on non/semi-polar substrate. Non-polar and semi-polar GaN layers were grown onto patterned sapphire substrates (PSS) and nano-porous GaN/sapphire substrates, respectively. Using PSS with the hemispherical patterns, we could achieve high luminous intensity. In case of semi-polar GaN, photo-enhanced electrochemical etching (PEC) was applied to make porous GaN substrates, and semi-polar GaN was grown onto nano-porous substrates. Our results showed the improvement of device characteristics as well as micro-structural and optical properties of non-polar and semi-polar GaN. Patterning and nano-porous etching technologies will be promising for the fabrication of high efficiency non-polar and semi-polar InGaN LED on sapphire substrate.

• 전자공학회논문지 IE
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• 제43권2호
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• pp.7-10
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• 2006

일반적인 산화 절연 게이트 대신 $BaTa_2O_6$를 사용한 GaN metal-insulator-semiconductor(MIS) 구조를 제작하였다. $Al_2O_3$(0001) 기판 위에서와 GaAs(001) 기판 위에서의 GaN 막의 누설 전류는 각각 $10^{-12}-10^{-13}A/cm^2$와 $10^{-6}-10^{-7}A/cm^2$로 측정되었다. 이 막의 누설전류는 각각 $Al_2O_3$(0001) 기판 위의 GaN인 경우는 45 MV/cm가 넘는 공간전하 제한전류에 의하여, GaAs(001) 기판 위의 GaN인 경우는 Poole-Frenkel 방출에 따른다는 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제21권1호
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• pp.5-11
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• 2008

To study the effects of $H_2$ gas on AIN insulation thin film, we prepared AIN thin film on Si and GaAs substrate by means of reactive sputtering method using $H_2$ gas as an additives, With treatment conditions of $H_2$ gas AIN thin film shows variable electrical properties such as its crystallization and hysterisis affected to electrical property, As a results, AIN thin film fabricated on Si substrate post-treated with $H_2$ gas for 20 minutes shows much better an insulation property than that of pre-treated, And AIN film treated with $H_2$ gas comparing to non-treated AIN film shows a flat band voltage decreasment. But In GaAs substrate $H_2$ gas does not effect on the flat band voltage.

• 한국전기전자재료학회논문지
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• 제30권12호
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• pp.794-799
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• 2017

Ga-doped ZnO (GZO) films were deposited by an RF magnetron sputtering method on glass substrates using ZnO as a target containing 5 wt% $Ga_2O_3$ powder (for Ga doping). The structural, electrical, and optical properties of the GZO thin films were investigated as a function of the substrate temperatures. The deposition rate decreased with increasing substrate temperatures from room temperature to $350^{\circ}C$. The films showed typical orientation with the c-axis vertical to the glass substrates and the grain size increased up to a substrate temperature of $300^{\circ}C$ but decreased beyond $350^{\circ}C$. The resistivity of GZO thin films deposited at the substrate temperature of $300^{\circ}C$ was $7{\times}10^{-4}{\Omega}cm$, and it showed a dependence on the carrier concentration and mobility. The optical transmittances of the films with thickness of $3,000{\AA}$ were above 80% in the visible region, regardless of the substrate temperatures.