MBE of GaN with DC-plasma source for nitrogen activation

In this paper we report on the first results of epitaxial growth of GaN layers on GaAs (100) substrates using a modified MBE system, equipped with a DC-plasma source for nitrogen activation in configuration of reverse magnetron at ultra-low pressures.

注入锁定掺铒光纤环形腔激光器及波长调谐技术

研究了掺铒光纤环形腔激光器（EDFRL）的注入锁定现象，提出了一种实现可调谐的单纵模EDFRL波长及功率稳定的新方法，即利用注入锁定技术向法布里．珀罗可调滤波器结合复合腔结构的EDFRL腔内注入低功率的连续光，使某一纵模在注入连续光的基础上起振．这个纵模在对增益介质的竞争中可以稳定地占据优势，从而与注入信号发生锁定，实现激光器输出光谱的稳定．实验得到激光器在1527．4～1561．9nm范围内波长可调，输出功率〉0．6dBm，信噪（SNR）〉43dB；输出光波长与功率抖动分别〈0．01nm和≤0．02dB，且线宽约为1.4kHz。

低能离子束制备(Ga,Gd,As)薄膜

室温条件下,用离子束外延设备制备(Ga,Gd,As)样品,X射线衍射(XRD)结果表明除了GaAs衬底峰,没有发现其他新相的衍射峰.俄歇电子能谱(AES)分析了样品中元素随深度的变化,不同样品中元素的分布有着不同的特点.并运用原子力显微镜(AFM)研究了样品表面的形貌特点,表明样品表面的粗糙度与Gd注入过程中在样品表面沉积的多少有关.运用交变梯度磁强计(AGM)对薄膜进行磁性分析,结果表明有的样品在室温条件下出现铁磁性,但金属钆本身具有室温铁磁性,因而需要进一步分析.

低阈值InGaAs-GaAs应变层多量子阱激光器

于2010-11-23批量导入

Effects of polarization field on formation of two-dimensional electron gas in (0001) and (11(2)over-bar0) plane AlGaN/GaN heterostructures

Photoluminescence (PL) and temperature-dependent Hall effect measurements were carried out in (0001) and (11 (2) over bar0) AlGaN/GaN heterostructures grown on sapphire substrates by metalorganic chemical vapor deposition. There are strong spontaneous and piezoelectric electric fields (SPF) along the growth orientation of the (0001) AlGaN/GaN heterostructures. At the same time there are no corresponding SPF along that of the (1120) AlGaN/GaN. A strong PL peak related to the recombination between two-dimensional electron gas (2DEG) and photoexcited holes was observed at 3.258 eV at room temperature in (0001) AlGaN/GaN heterointerfaces while no corresponding PL peak was observed in (11 (2) over bar0). The existence of a 2DEG was observed in (0001) AlGaN/GaN multi-layers with a mobility saturated at 6000 cm(2)/V s below 80 K, whereas a much lower mobility was measured in (11 (2) over bar0). These results indicated that the SPF was the main element to cause the high mobility and high sheet-electron-density 2DEG in AlGaN/GaN heterostructures. (C) 2004 Elsevier B.V. All rights reserved.

Optical study on the coupled GaAsSb/GaAs double quantum wells

The structural and optical properties of GaAsSb/GaAs-based quantum wells (QWs) are investigated. The interface quality of GaAsSb/GaAs/GaAsP coupled double (CD) QW structures is improved due to the strain compensation of epitaxial layers. The CD QWs possess a W-shape of energy band structure, and the optical properties display the features characteristic of a type-IQW when the GaAsSb layer thickness is thin enough.

Raman scattering and infrared absorption of silicon nanocrystals in silicon oxide matrix

Structural dependence on annealing of a-SiOx:H was studied by using infrared absorption and Raman scattering. The appearance of Raman peaks in the range of 513-519cm(-1) after 1170 degreesC annealing was interpreted as the formation nanocrystalline silicon with the sizes from 3-10nm. The Raman spectra also show the existence of amorphous-like silicon phase, which is associated with Si-Si bond re-construction at boundaries of silicon nanocrystallites. The presence of the shoulder at 980cm(-1) of Si-O-Si stretching vibration at 1085cm(-1) in infrared spectra imply that except that SiO2 phase, there is silicon sub-oxide phase in the films annealed at 1170 degreesC. This sub-oxide phase is located at the interface between Si crystallites and SiO2, and thus support the shell model for the mixed structures of Si grains and SiO2 matrix.

Mechanism on exciton-mediated energy transfer in erbium-doped silicon

Exciton-mediated energy transfer model in Er-doped silicon was presented. The emission intensity is related to optically active Er concentration, lifetime of excited Er3+ ion and spontaneous emission. The thermal quenching of the Er luminescence in Si is caused by thermal ionization of Er-bound exciton complex and nonradiative energy back-transfer processes, which correspond to the activation energy of 6.6 and 47.4 meV, respectively. Er doping in silicon introduces donor states, a large enhancement in the electrical activation of Er (up to two orders of magnitude) is obtained by co-implanting Er with O. It appears that the donor states are the gateway to the optically active Er. (C) 2000 Elsevier Science B.V. All rights reserved.