光注入对半导体激光器非线性特性的影响研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-21T07:33:37Z No. of bitstreams: 1 李伟—博士论文.pdf: 2980910 bytes, checksum: 5bad5e21fcd02d255983a1c8d5ee7f29 (MD5)

In(Ti,Sn)-O 与Sn(Pb)Zn-Te 的电子结构研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-07-21T01:27:16Z No. of bitstreams: 1 出站报告唐黎明.pdf: 6269250 bytes, checksum: 868d0cf22419850e8dcb1acba888aeb9 (MD5)

Spin injection in the multiple quantum-well LED structure with the Fe/AlO (x) injector

A spin-injection/-detection device has been fabricated based on the multiple quantum well light emitting diode (LED) structure. It is found that only a broad electroluminescence (EL) peak of a full width at half maximum of 8.6 nm appears at the wavelength of 801 nm in EL spectra with a circular luminescence polarization degree of 18%, despite PL spectra always show three well resolved peaks. The kinetic energy gained by injected electrons and holes in their drift along opposite directions broadens the EL peak, and makes three EL peaks converge together. The same process also destroys the injected spin polarization of electrons mainly dominated by the Bir-Aronov-Pikus spin relaxing mechanism.

金属限制正方形微腔激光器的研究与制作

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-07-02T05:57:38Z No. of bitstreams: 1 车凯军-博士论文.pdf: 4914653 bytes, checksum: dcdc84df1fdc7b8c52bb7485c2382968 (MD5)

Origin of antiferromagnetism in CoO: A density functional theory study

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-05-07T13:34:11Z No. of bitstreams: 1 Origin of antiferromagnetism in CoO A density functional theory study.pdf: 263570 bytes, checksum: 9128a541375fb9fe9f761fc02ece4210 (MD5)

宽禁带半导体纳米结构中缺陷和掺杂特性研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-09-08T01:31:21Z No. of bitstreams: 1 王治国_博士后出站报告.pdf: 51512790 bytes, checksum: efccdb1a25bf8cdc9d51efe28a116ff4 (MD5)

Theoretical gain of strained GeSn0.02/Ge1-x-y ' SixSny ' quantum well laser

Using effective-mass Hamiltonian model of semiconductors quantum well structures, we investigate the electronic structures of the Gamma-conduction and L-conduction subbands of GeSn/GeSiSn strained quantum well structure with an arbitrary composition. Our theoretical model suggests that the band structure could be widely modified to be type I, negative-gap or indirect-gap type II quantum well by changing the mole fraction of alpha-Sn and Si in the well and barrier layers, respectively. The optical gain spectrum in the type I quantum well system is calculated, taking into account the electrons leakage from the Gamma-valley to L-valley of the conduction band. We found that by increasing the mole fraction of alpha-Sn in the barrier layer and not in the well layer, an increase in the tensile strain effect can significantly enhance the transition probability, and a decrease in Si composition in the barrier layer, which lowers the band edge of Gamma-conduction subbands, also comes to a larger optical gain.

光子晶体慢光波导的结构设计与特性分析

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-07-12T02:14:34Z No. of bitstreams: 1 曲连杰--光子晶体慢光波导的结构设计与特性分析.pdf: 2968554 bytes, checksum: 139f77baccde2ed4370e42b8c076c944 (MD5)

Fe/Al2O3/(GaAs/AlAs)多量子阱结构中的自旋滤波现象研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-10-11T08:04:28Z No. of bitstreams: 1 李韫慧--毕业论文.pdf: 3605559 bytes, checksum: 42b64ac7c4003c8c729c7aa5a941791e (MD5)

Ultrafast photo-induced turning of magnetization and its relaxation dynamics in GaMnAs

We report that, by linearly polarized pumping of different wavelengths, Kerr transients appear at zero magnetic field only in the case when GaMnAs samples are initialized at 3 K by first applying a 0.8 Tesla field and then returning to zero field. We find that, instead of magnetization precession, the near-band gap excitation induces a coherent out-of-plane turning of magnetization, which shows very long relaxation dynamics with no precession. When photon energy increases, the peak value of the Kerr transient increases, but it decays rapidly to the original slow transient seen under the near-band-gap excitation.

半导体微腔激光器和光学双稳态的研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-07-12T02:26:44Z No. of bitstreams: 1 微腔激光器及光学双稳态研究—王世江.pdf: 4728351 bytes, checksum: 4a0251670e5c287ad8fc6ec54065b016 (MD5)

STUDY ON MICROWAVE CYCLOTRON RESONANCE OF HIGH-MOBILITY GaAs/Al-0.35 Ga-0.65 As TWO-DIMENSIONAL ELECTRON GAS

The properties of electron states in the presence of microwave irradiation play a key role in understanding the oscillations of longitudinal resistance and the zero-resistance states in a high-mobility two-dimensional electron gas(2DEG) in low magnetic field. The properties of electron states in a high-mobility and low-density GaAs/Al0.35Ga0.65As 2DEG in the presence of Ka-band microwave irradiation were studied by reflectance-based optically detected cyclotron resonance(RODCR). The influences of the direction of microwave alternating electronic field, wavelength of the laser, and temperature on RODCR results were discussed. The results show that RODCR measurements provide a convenient and powerful method for studying electron states in 2DEG.

Study of GaN epilayers growth on freestanding Si cantilevers

Five-micron thick freestanding Si cantilevers were fabricated on bulk Si (1 1 1) substrates with surface/bulk micromachining (SBM) process. Then 1-mu m thick GaN layers were deposited on the Si cantilevers by metal-organic chemical vapor deposition (MOCVD). Epilayers on cantilever areas were obtained crack-free, and the photoluminescence (PL) spectra verified the stress reduction and better material quality in these suspended parts of GaN. Back sides of the cantilevers were also covered with GaN layers, which prevented the composite beams from bending dramatically. This paper had proved the feasibility of integrating high-quality GaN epilayers with Si micromechanical structures to realize GaN-based micro electro-mechanical system (MEMS). (C) 2009 Elsevier Ltd. All rights reserved.

Donor-donor binding in In2O3: Engineering shallow donor levels

Using first-principles band structure methods, we investigate the interactions between different donors in In2O3. Through the formation energy and transition energy level calculations, we find that an oxygen-vacancy creates a deep donor level, while an indium-interstitial or a tin-dopant induces a shallow donor level. The coupling between these donor levels gives rise to even shallower donor levels and leads to a significant reduction in their formation energies. Based on the analysis of the PBE0-corrected band structure and the molecular-orbital bonding diagram, we demonstrate these effects of donor-donor binding. In addition, total energy calculations show that these defect pairs tend to be more stable with respect to the isolated defects due to their negative binding energies. Thus, we may design shallow donor levels to enhance the electrical conductivity via the donor donor binding.

An experimental study about the influence of well thickness on the electroluminescence of InGaN/GaN multiple quantum wells

The influence of well thickness on the electroluminescence (EL) of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition is investigated. It is found that the peak wavelength of EL increases with the increase of well thickness when the latter is located in the range of 3.0-5.1 nm. The redshift is mainly attributed to the quantum confined Stark effect (QCSE). As a contrast, it is found that the EL intensity of InGaN/GaN MQWs increases with the increase of well thickness in spite of QCSE. The result of X-ray diffraction demonstrates that the interface become smoother with the increase of well thickness and suggests that the reduced interface roughness can be an important factor leading to the increase of EL intensity of InGaN/GaN MQWs. (C) 2009 Elsevier B.V. All rights reserved.