• 한국결정성장학회지
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• 제32권2호
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• pp.45-50
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• 2022

유기금속 화학 증착 방법(MOCVD)을 사용하여 Si 기판 위에 Ga₂O₃ 박막들을 다양한 성장 온도에서 형성하였다. 성장 온도 500℃와 550℃에서 성장한 Ga₂O₃ 박막들은 매우 깨끗하고 평평한 표면 상태를 보였으며, 결정구조는 비정 질 상태임을 확인할 수 있었다. 성장한 박막들의 열처리 효과를 확인하기 위하여 각각의 박막들은 900℃ 온도에서 10분간 열처리를 수행하였다. 성장 온도 500℃와 550℃에서 성장한 박막들은 초기의 평평한 표면 상태는 그대로 유지하면서 결정 구조가 비정질에서 다결정으로 변한 것을 확인할 수 있었다. 쇼트키 다이오드를 제작하기 위한 박막으로는 550℃에서 성장한 박막을 선택하였는데, 이는 소자의 제작 및 성능을 향상하기 위해서는 평평한 표면 위에서의 공정이 필수적이기 때문이다. 또한, 열처리 효과를 확인하기 위하여 900℃에서 열처리를 실시한 박막을 이용하여 동일한 형태의 쇼트키 다이오드를 제작하여 특성을 비교하였다. 또한 박막의 광소자로의 응용 가능성을 확인하기 위하여 MSM(metal-semiconductor-metal) 광검출기를 제작한 결과 266 nm 자외선 파장의 빛에 대응하는 광전류(동작 전압 10 V)는 암전류 대비 약 5.32배 증가함을 보이는 것을 확인하였다.

• 대한전자공학회논문지SD
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• 제49권2호
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• pp.15-22
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• 2012

본 논문에서 공핍 모드 n-채널 InGaZnO 박막트랜지스터를 이용하여 소비전력이 낮은 스캔 구동 회로를 제안한다. 제안된 스캔 구동 회로는 단 2개의 클록 신호만을 사용하고 추가적인 마스킹 신호나 회로가 필요 없이 이웃하는 스캔 출력 간에 겹쳐짐이 없는 스캔 출력 신호를 만들어 낸다. 클록 신호를 줄임과 동시에 단락 전류를 줄임으로써 소비전력을 줄일 수 있었다. 모의 실험 결과 트랜지스터 문턱전압의 편차 범위가 -3.0 ~ 1.0V일 때에도 스캔 출력 신호가 정상적으로 출력됨을 확인하였다. XGA의 해상도를 갖는 디스플레이를 대상으로 양과 음의 전원 전압이 각각 15V, -5V이고 동작 주파수가 46KHz일 때, 스캔구동 회로의 소비전력이 4.89mW이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.184-184
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• 2012

Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.

• 대한기계학회논문집A
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• 제29권4호
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• pp.632-638
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• 2005

The surface lapping process on sapphire wafer was carried out for the epitaxial process of thin film growth of GaN semiconducting material. The planarization of the wafers was investigated by the introduction of the dummy wafers. The diamond lapping process causes the surface deformation of dislocation and micro-cracks. The material deformation due to the mechanical stress was analyzed by the X-ray diffraction and the Vickers indentation. The fracture toughness was increased with the increased annealing temperature indicating the recrystallization at the surface of the sapphire wafer The sudden increase at the temperature of $1200^{\circ}C$ was correlated with the surface phase transition of sapphire from a $-A1_{2}O_{3}\;to\;{\beta}-A1_{2}O_{3}$.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1632-1639
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• 2004

Numerical calculation has been performed to investigate the transport phenomena in the horizontal reactor which has two different gas inlets for MOCVD(metalorganic chemical vapor deposition). The full elliptic governing equations for continuity, momentum, energy and chemical species are solved by using the commercial code FLUENT. It is investigated how thermal characteristics, reactor geometry, and the operating parameters affect flow fields, mass fraction of each reactants. The numerical simulations demonstrate that flow rate of each species, inlet geometry of the reactor, and its distance from the susceptor as well as the inclination of upper wall of reactor can be used effectively to optimize reactor performance. The commonly used idealized boundary conditions are also investigated to predict flow phenomena in the actual deposition system.

• 한국전기전자재료학회논문지
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• 제20권1호
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• pp.8-13
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• 2007

In MIS capacitor structure, we have studied the electrical properties in Ammonium Sulfide solution treatment while AIN thin film as a insulator is being formed by reactive sputtering method. The deposition process conditions of AIN thin film we temperature $250^{\circ}C$, DC Power 150 W, pressure 5 mTorr and 8 sccm(Ar : 4 sccm, $N_{2}$ : 4 sccm). The surface of GaAs was treated with Ammonium Sulfide solution, it was shown the leakage current was less than $10^{-8}\;A/cm^{2}$. The deep depletion phenomena of inverse area with treating Ammonium Sulfide solution in C-V analysis was improved as compared the condition of without Ammonium Sulfide solution and hysteresis property as well.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.122-123
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• 2007

Single crystal $AgGaSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_2$ source at $630^{\circ}C$. The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T)=1.9501 eV - $(8.79{\times}10^{-4}\;eV/K)T^2$/(T+250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_2$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $AgGaSe_2$. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{1^-}$exciton peaks for n=1.

• 한국재료학회지
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• 제11권7호
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• pp.575-579
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• 2001

Metal organic chemical vapor deposition (MOCVB)법을 사용하여 sapphire (0001) 기판 위에 GaN 환충층을 성장하고, 그 위에 GaN 에피층을 성장하였다. GaN 완충층은 55$0^{\circ}C$에서 약 26 nm에서 130 nm까지 각각 다른 두께로 성장하였고, GaN 에피층은 110$0^{\circ}C$에서 약 4 $\mu\textrm{m}$의 두께로 성장하였다. GaN 완충층 성장 후 atomic force microscopy (AFM)으로 표면 형상을 측정하였다. GaN 완충층의 두께가 두꺼워질수록 GaN 에피층의 표면이 매끈해지는 것을 scanning electron microscopy (SEM)으로 관찰하였다. 이것으로 GaN 에피층의 표면은 완충층의 두께와 표면 거칠기와 관계가 있다는 것을 알 수 있었다. GaN 에피층의 결정학적 특성을 double crystal X-ray diffraction (DCXRD)와 Raman spectroscopy로 측정하였다. 성장된 GaN 에퍼층의 광학적 특성을 photoluminescence (PL)로 조사한 결과 두께가 두꺼운 완충층 위에 성장된 에퍼층의 결정성이 더 좋은 반면, 내부 잔류응력은 증가하는 결과를 보였다. 이러한 사실들로부터 완충층의 두께가 두꺼워짐에 따라 내부 자유에너지가 감소하여 에피층 성장시 측면성장을 도와 표면이 매끈해지고, 결정성이 좋아졌다.

• 한국전기전자재료학회논문지
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• 제21권4호
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• pp.329-334
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• 2008

Aluminum oxide films were deposited on n-type GaN substrates by RF magnetron sputtering technique for MIS devices applications using optimized conditions, Well-behaved C - V characteristics were obtained measured in MIS capacitors structures. The calculated interface trap density measured at $300^{\circ}C$ was about $9\times10^{10}/cm^2$ eV in the upper bandgap. The gate leakage current densities of the MIS structures were about $10^{-9}A/cm^2$ and about $10^{-4}A/cm^2$ measured at room temperature and at $300^{\circ}C$ for $a{\pm}1MV/cm$, respectively. These results indicate that the interface property of this structure is enough quality to MIS devices applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.468-470
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• 1999

One of the most critical problem in etching of platinum was generally known that the etch slope was gradual. therefore, the addition of $N_2$ gas into the Ar/C1$_2$ gas mixture, which has been proposed the optimized etching gas combination for etching of platinum in our previous article, was performed. The selectivity of platinum film to oxide film as an etch mask increased with the addition of N2 gas, and the steeper etch slope over 75 $^{\circ}$ could be obtained. These phenomena were interpreted the results the results of a blocking layer such as Si-N or Si-O-N on the oxide mask. Compostional analysis was carried out by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Moreover, it could be obtained the higher etch rate of Pt film and steeper profile without residues such as p.-Cl and Pt-Pt ant the addition N\ulcorner of 20 % gas in Ar(90)/Cl$_2$(10) Plasma. The Plasma characteristic was extracted from optical emissionspectroscopy (OES).