Optical gain in zinc-blende GaN/Ga1-xAlxN strained quantum well laser

Based on the valence subbands of the zinc-blende GaN/Ga0.85Al0.15N strained quantum wells obtained by a 6x6 Hamiltonian (including heavy hole, light hole and spin-orbit splitting band), optical gain and radiative current density are calculated for the strained quantum well laser structures. The compressive strain in the GaN well region strongly depresses the TM mode optical gain and enhances the TE mode optical gain.

GaN横向外延中晶面倾斜的形成机制

采用双晶X射线衍射（DC－XRD）研究蓝宝石（0001）衬底上横向外延GaN层中晶面倾斜的形成原因。发现横向生长区的GaN在垂直掩模方向上朝SiNx掩模层弯曲。采用选择性腐蚀逐渐去掉SiNx掩模层，发现XRD中G N(002)ω扫描衍射峰两侧存在与晶面倾斜有关的衍射信息。该衍射信息起初为一个很宽的峰，随着选择性腐蚀的进行，会先分裂为两个峰，最后当SiNx掩模层全部腐蚀掉后，其中一个衍射峰会消失，而只剩下一个很窄的峰。作者证实造成横向外延GaN中晶面倾斜的原因有两个

Influence of In0.2Ga0.8As strain-reducing layer on the active region of quantum dot superluminescent diodes

We have investigated the optical properties of asymmetric multiple layer stacked self-assembled InAs quantum dot with different interlayer. We found that asymmetric multiple stacked QD samples with In0.2Ga0.8As + GaAs interlayer can afford a 180nm flat spectral width with strong PL intensity compared to other samples at room temperature. We think this result is due to the introduction of In0.2Ga0.8As strain-reducing layer. Additionally, for the broad spectral width and the strong PL intensity, this structure can be a promising candidate for quantum-dot superluminescent diodes.

Polymorphous silicon nanowires synthesized by plasma-enhanced chemical vapor deposition

Polymorphous Si nanowires (SiNWS) have been successfully synthesized on Si wafer by plasma enhanced chemical vapor deposition (PECVD) at 440degreesC,using silane as the Si source and Au as the catalyst. To grow the polymorphous SiNWS preannealing the Si substrate with Au film at 1100 degreesC is needed. The diameters of Si nanowires range from 15 to 100 urn. The structure morphology and chemical composition of the SiNWS have been characterized by high resolution x-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as energy dispersive x-ray spectroscopy. A few interesting nanowires with Au nanoclusters uniformly distributed in the body of the wire were also produced by this technique.

Microstructure of the silicon film prepared near the phase transition regime from amorphous to nanocrystalline

A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) near the phase transition regime from amorphous to nanocrystalline. The microstructural properties of the films have been investigated by the micro-Raman and Fourier transformed Infrared (FT-IR) spectra and atom force microscopy (AFM). The obtained Raman spectra show not only the existence of nanoscaled crystallites, but also a notable improvement in the medium-range order of the diphasic films. For the FT-IR spectra of this kind of films, it notes that there is a blueshift in the Si-H stretching mode and a redshift in the Si-H wagging mode in respect to that of typical amorphous silicon film. We discussed the reasons responsible for these phenomena by means of the phase transition, which lead to the formation of a diatomic hydrogen complex, H-2* and their congeries.

Formation mechanism of electric field domains

Hydrostatic pressure measurements are used to investigate the formation mechanism of electric field domains in doped weakly-coupled GaAs/AlAs superlattices. For the first plateau-like region in the I-V curve, two kinds of sequential resonant tunnelling are observed. For P<2 kbar the high-field domain is formed by the Gamma-Gamma process, while for P>2 kbar the high-field domain is formed by the T-X process. For the second plateau-libe region, the high-field domain is attributed to Gamma-X sequential resonant tunnelling. (C) 1998 Elsevier Science B.V. All rights reserved.