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아르곤 플라즈마로 처리한 n - GaAs의 표면특성에 관한 Photoreflectance 연구
이동율(Dong-Yul Lee),김인수(In-Soo Kim),김동렬(Dong-Lyeul Kim),김근형(Geun-Hyoung Kim),배인호(In-Ho Bae),김규호(Kyoo-Ho Kim),한병국(Byung-Kuk Han) 한국진공학회(ASCT) 1997 Applied Science and Convergence Technology Vol.6 No.4
Power를 40 W로 고정하고 시간을 5~120초간 변화시켜 아르콘 플라즈마로 처리시킨 n-GaAs(100)의 특성을 photoreflectance(PR) 측정으로 조사하였다. 아르곤 플라즈마 처리시간을 증가시킴에 따라 E。 피크의 세기는 처리시간이 5초일 때 최소로 관측되었으며, 이때 표면전기장(E_S), 순수 캐리어농도(N_D-N_A) 및 표면상태 밀도 (Q_(SS))는 각각 1.05×10^5 V/㎝, 1.31×10^(17) ㎝-³ 및 1.64×10^(-7) C/㎡로 이 값들은 bulk 시료에 비해 약 57.1, 81.4 및 56.9% 감소하였다. 반면에 5초일 때 compensation center 농도(N_A)는 5.57×10^(17) ㎝-³로 최대였다. 그리고 아르곤 플라즈마 처리시 유발된 결함들의 침투깊이는 표면에서 약 450 Å 정도였다. We have investigated the surface characteristics of n-GaAs (100) treated with Ar plasma (40 W, 5~120 sec) by photoreflectance (PR) measurement. With increasing Ar plasma treatment time, the intensity of E。 peak observed to the minimum at 5 sec. The surface electric field (E_S), net carrier concentration (N_D-N_A), and surface state density (Q_(SS)) are 1.05×10^5 V/㎝, 1.31×10^(17) ㎝-³ and 1.64×10^(-7) C/㎡, respectively. These values were about 57.1, 81.4 and 56.9% smaller than those of bulk n-GaAs. On the other hand, the concentration of compensation centers (N_A) was maximum with value of 5.57×10^(17) ㎝-³ at 5 sec. And penetration depth of defects generated after treated with Ar plasma was about 450 Å from surface.
분자선 에피탁시법으로 성장된 Al0.25Ga0.75As / In0.15Ga0.85As / GaAs 슈우도형 고 전자 이동도 트랜지스터 구조의 광학적 특성
이동율(Dong-Yul Lee),이철욱(Chul-Wook Lee),김기홍(Ki-Hong Kim),김종수(Jong-Su Kim),김동렬(Dong-Lyeul Kim),배인호(In-Ho Bae),전헌무(Hunmoo Jeon),김인수(In-Soo Kim) 한국진공학회(ASCT) 2000 Applied Science and Convergence Technology Vol.9 No.2
Photoluminescence(PL)와 photoreflectance(PR}를 이용하여 Al_(0.25)Ga_(0.75)As/In_(0.15)Ga_(0.85)As/GaAs 슈우도형 고 전자 이동도 트랜지스터 구조에 대한 특성을 조사 하였다. 온도 10 K의 PL 측정에서 InGaAs 양자우물에 의한 e2-h1 및 e2-h1 전이 피크가 각각 1.322 및 1.397 eV에서 관측되었다. 온도 의존성으로부터 첫번째 가전자 띠와 두번째 가전자 띠의 에너지 차이는 약 23 meV로 나타났다. 또한 300 K에서의 PR 측정으로 e2-h2 및 e2-h1 전이에 의한 피크를 관측하였고, 두번째 전도 띠의 에너지 준위에 의한 피크가 띠 채움으로 인해 첫번째 전도 띠의 에너지 준위에 의한 피크보다 상대적으로 우세하였다. 반면에 PL 측정에서는 전자 가리개 효과 때문에 첫번째 전도 띠에 의한 피크가 우세하였다. We have analyzed characteristics for the structure of Al_(0.25)Ga_(0.75)As / In_(0.15)Ga_(0.85)As/GaAs pseudo-morphic high electron mobility transistor (PHEMT) by photoluminescence (PL) and photoreflectance (PR) measurements. By the PL measurement at 10 K, we observed e1-h1 transition peak at 1.322 eV and e2-h1 transition peak at 1.397 eV in the InGaAs quantum well. We calculated value of 23 meV, the difference between the first energy level and the second energy level of a valence band by dependence of temperatures. Also, (e2-h2) transition signal was observed at 300 K by PR measurement. From the PR measurement, we recognized that the transition was dominated the second energy level of conduction band than the first energy level of conduction band due to band filling. The other hand, PL signal of the first energy level of conduction band was dominated because of the electron screening effect.
Photoreflectance 측정에 의한 In0.1Ga0.9As / GaAs 계면의 특성 조사
이철욱(Chul-Wook Lee),김인수(In-Soo Kim),손정식(Jeong-Sik Son),김동렬(Dong-Lyeul Kim),임재영(Jae-Young Leem),배인호(In-Ho Bae) 한국진공학회(ASCT) 1997 Applied Science and Convergence Technology Vol.6 No.3
In_(0.1)Ga_(0.9)As/GaAs의 계면 특성을 상온에서 photoreflectance(PR) 측정을 통하여 연구하였다. 에피층의 두께가 증가함에 따라 PR 신호에서 Franz-Keldysh oscillation(FKO)의 주기가 감소하였고, 계면 전기장은 감소되었다. 이것은 InGaAs와 GaAs의 이종정합계면 부근에서 격자부정합에 의한 결함이 증가되었기 때문으로 생각된다. 에피층의 두께가 300 Å보다 적은 경우 두께가 얇아짐에 따라 InGaAs 층이 임계 두께에 가까워져 strain의 영향으로 밴드갭 에너지가 크게 이동하였다. We studied an interfacial characteristics of In_(0.1)Ga_(0.9)As/GaAs by photoreflectance (PR) measurement at room temperature. With increasing thickness of epitaxial layer, Franz-Keldysh oscillation (FKO) periods of PR signals were decreased, and interfacial electric field was decreased. This can be explained by the increase of defects due to lattice mismatch near the heterointerface between InGaAs and GaAs. For the thickness of epitaxial layer thinner than the 300 Å, InGaAs epitaxial layer closed to critical thickness and increased strain, and then the bandgap energy shifted high energy greatly.
MBE 법으로 성장시킨 AlxGa₁-xAs 에피층의 Photoreflectance 특성에 관한 연구
이정열(Jung-Yeul Lee),김인수(In-Soo Kim),손정식(Jeonng-Sik Son),김동렬(Dong-Lyeul Kim),배인호(In-Ho Bae),김대년(Dae-Nyoun Kim) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.4
MBE법에 의해 성장된 Al_xGa_(1-x)As 에피층의 특성을 photoreflectance(PR) 측정으로 분석하였다. Low power Franz Keldysh(LPFK)를 만족하는 GaAs 완충층에 의한 Frang-Keldysh Oscillation(FKO) 분석에서 띠 간격에너지(E。) 값은 1.415 eV, 계면 전기장(E_i)은 1.05×10⁴V/㎝, 운반자 농도(N_s)는 1.3×10^(15) ㎝-³ 이였다. PR 상온 스펙트럼 분석에서 Eo(Al_xGa_(1-x)As) 신호 아래 A^* 피크는 시료 성장시 존재하는 불순물 carbon에 의한 것으로 완충층 GaAs 보다 다소 PR 신호 세기가 낮고 왜곡된 신호를 나타내었다. 또한, GaAs 완충층의 트랩 특성시간은 약 0.086 ㎳ 정도이며, 1.42 eV 부근 두 개의 중첩된 PR 신호는 화학적 식각으로 GaAs의 기판에 의해 나타나는 3차 미분형 신호와 GaAs 완충층에 의해 나타나는 FKO 신호가 중첩되어 나타남을 알 수 있었다. We analyzed photoreflectance (PR) characterization of the Al_xGa_(1-x)As epilayer grown by molecular beam epitaxy (MBE) method. The band-gap energy (E。) satisfying low power Franz-Keldysh (LPFK) due to GaAs buffer layer is 1.415 eV, interface electrical field (E_i) is 1.05×10⁴V/㎝, carrier concentration (N) is 1.3×10^(15) ㎝-³. In PR spectrum intensity analysis at 300 K the A^* peak below E。 signal is low and distorted because of residual impurity in sample growth. The trap characteristic time (τ_i) of GaAs buffer layer is about 0.086 ㎳, and two superposed PR signal near 1.42 eV consist of the third derivative signal of chemically etched GaAs substrate and Franz-Keldysh oscillation (FKO) signal due to GaAs buffer layer.
Photoreflectance 및 Photocurrent 측정에 의한 반절연성 GaAs의 광학적 특성
김기홍,김동렬,배인호,김대년,김인수 嶺南大學校 基礎科學 硏究所 1998 基礎科學硏究 Vol.18 No.-
We report on the room temperature optical characterization of semi-insulating GaAs. The energy gap of semi-insulating GaAs was determined to be 1.41eV by photoreflectance(PR)and possible orgin of the photoreflectance signal is discussed. From photoreflectance(PC)measurement, the peak of PC is observed at 1.40 eV, corresponding to GaAs band to band transition. The influence of temperature and dependent upon the chopper frequency on the PC of semi-insulating GaAs is studied.
Al_(0.3)Ga_(0.7)As/GaAs 다중 양자우물구조에서 Photolumunescence의 온도 의존성
김동렬,배인호,김대년,박성배,신영남 大邱大學校附設 基礎科學硏究所 1998 基礎科學硏究 Vol.15 No.1
Temperature dependent photoluminescence(PL) has been applied to characterize the subband transition in Al_(0.3)Ga_(0.7)As/GaAs multiple quantum wells grown by molecular beam epitaxy. The PL signal at 295 K showed main peak located at 1.4795 eV with a shoulder around 1.4973 eV. They are associated with the E1 H1 and E1 L1. From temperature dependent PL intensity, activation energy is determined to be 22 meV. From temperature dependent PL linewidth, γ_(i) and γ_(c) are determined to be 5.26±0.2 meV, 136±52 meV, respectively. When the lattice temperature was decreased, the peak energy increased, following the temperature dependence of the bulk GaAs band gap, down to around 30 K, and then deviated to the lower energy side by about 3.5 meV at 12 K.
(GaAs)m/(AlAs)m 단주기 초격자의 Crossover에 대한 연구
김동렬,배인호 嶺南大學校 基礎科學硏究所 1996 基礎科學硏究 Vol.16 No.-
Photoluminescence measurement is carried out to clarify the crossover from the direct to the indirect transition in ??/?? short-period superlattices(SPS) with m=15 from m=1. Energy band calculation based on the envelope function approximation shows a good agreement with the experimental observation, where ??/?? short-period superlattices are of indirect gap material for m≤12 and direct gap material for m>12.
MBE(molecular beam epitaxy)로 성장된 GaAs/AlAs 초격자의 특성연구
김동렬,김말문 嶺南大學校 基礎科學硏究所 1996 基礎科學硏究 Vol.16 No.-
GaAs/AlAs superlattice was grown by molecular beam epitaxy with a thickness of 15 monolayers. We have performed photoluminescence measurement. Measurement were performed as a function of excitation laser power and temperature. The photoluminescence peak intensity as a function of excitation laser power is well described by a straight line on logarithmic plot, indicating that radiative recombination mechanism is excitonic-like transition. Finally, we have showed the temperature dependence of the peak energy of the HI-Cl transition. When lattice temperature was decreased, the peak energy first increased, following the temperature dependence of the bulk GaAs band gap, and deviated to the lower energy side by about 4 meV at 7.2K from extrapolated curve. The observed Stokes shift is in good agreement with previous results on multiple-quantum well sample of the high quality.