서지주요정보
Photoreflectance를 이용한 (Al,In)GaAs/GaAs 계에서의 계면구조의 관측과 광학적 특성에 관한 연구 = Observation of interface structure and optical properties of (Al,In)GaAs/GaAs heterojunctions systems
서명 / 저자 Photoreflectance를 이용한 (Al,In)GaAs/GaAs 계에서의 계면구조의 관측과 광학적 특성에 관한 연구 = Observation of interface structure and optical properties of (Al,In)GaAs/GaAs heterojunctions systems / 황인선.
발행사항 [대전 : 한국과학기술원, 1997].
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8007545

소장위치/청구기호

학술문화관(문화관) 보존서고

DPH 97015

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In this thesis, we reviewed the modulation mechanisms of the photoreflectance (PR) and investigated the optical properties of (Al,In)GaAs/ GaAs heterojunctions by photoreflectance. We observed the signal by the interfacial structures in PR spectra of InGaAs/GaAs and AlGaAs/GaAs heterostructures. Through the PR measurement of the selectively doped GaAs samples we suggested the hole-ionized acceptor(h-$A^{-}$) pair modulation mechanism for the first time. There are several modulation mechanisms in PR. Electric field modulation by photoinduced electrons and holes is a basic mechanism, and its PR signal has the third derivative functional form. The reflectivity is also changed by band filling effect of photoinduced carriers. This effect is confirmed by the PR of the heavily Si-doped GaAs samples. In addition, the PR can be affected by the spacial modulations of the critical point, such as exciton modulation, hole-ionized acceptor pair modulation, and impurity state modulation. The critical points, where excitons or hole-acceptor pairs are ionized by the built-in electric field and where an impurity level crosses the Fermi energy level, are changed as the electric field changes. The electric fields necessary to ionize excitons and hole-acceptor pairs are about 4 kV/cm and 300 kV/cm, respectively. We also observed the PR signals due to the transitions between excited states in quantum well structures. For InGaAs/GaAs heterostructures we observed a PR signal near 1.4 eV coming from the InGaAs/GaAs interfaces. And we suggested the possibility that there are metastable InGaAs clusters at the InGaAs/GaAs interface. While the double crystal x-ray diffraction data show that 15% compressive strain is remained in InGaAs epilayer, on an average, the PR data reveals that there are tensile-strained regions up to 67% in InGaAs layer. The residual tensile strain may be related to the clusters at the interface. The process, in which the strain relaxes, is also investigated; homogeneous relaxation → periodically inhomogeneous relaxation → inhomogeneous relaxation. In quantum well structure we comfirmed that symmetry forbidden transitions can be observed when the built-in electric field is sufficiently strong. In many reported PR spectra of modulation doped AlGaAs/GaAs heterostructures there are several discrepancies,(i) a broad PR signal or a step-like PR signal near the GaAs band edge, (ii) a single peak shape PR signal or a double peak shape(DPS) PR near the AlGaAs band edge, and (iii) a short period oscillation(SPO) PR signal is observed by a few authors only. By the PR measuerment of the etched sample we could know that the broad PR signal comes from the cap layer, while the steplike PR signal is due to the triangular potential well which has 2 dimensional electron gas, and that the higher energy signal of the DPS PR comes from the cap/n-AlGaAs interface. Through the annealing and the etching experiments we observed that there is an unknown PR signal near 1.5 eV and suggested the possibility for the existence of the interfacial structure at AlGaAs/GaAs interface. The built-in electric field is strengthened as the annealing time increases. This is an aging effect and results from the Si-Si pair diffusion. In PR spectra of the selectively doped GaAs samples the SPO signal is splitted into two distinct signals because of the high built-in electric field. We confirmed that these two signal are originated from the exciton and the hole-ionized acceptor pair modulation, respectively, through the investigation of the temperature dependance of the PR spectra.

서지기타정보

서지기타정보
청구기호 {DPH 97015
형태사항 xi, 112 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : In-Sun Hwang
지도교수의 한글표기 : 박해용
지도교수의 영문표기 : Hae-Yong Park
수록잡지명 : "Clustering effect and residual stress in InxGa1-xAs/GaAs strained layer grown by metal-organic chemical-vapor deposition". Physical Review B. American Physics Society, vol. 51, no. 12, pp. 7894-7897 (1995)
학위논문 학위논문(박사) - 한국과학기술원 : 물리학과,
서지주기 참고문헌 : p. 104-112
주제 Photoreflectance
Hole-acceptor pair modulation
Interface structure
2-dimensional electron gas(2DEG)
Heterojunction
High electron mobility transistor(HEMT)
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