WELL-WIDTH DEPENDENCE OF THE EXCITON LIFETIME IN GAAS/ALGAAS QUANTUM-WELLS

The dependence of the excitonic lifetime on the well width has been studied in conventional GaAs/AlGaAs quantum wells. Two clearly different variations of the measured excitonic lifetime have been observed. For wide well widths, we find a nearly linear decrease of the lifetime with decreasing well width. However, when the well is further decreased, a saturation and even increase of the lifetime with decreasing well width are observed. The experimental data are compared with the theory of radiative excitonic recombination, and show that well width dependence of the measured photoluminescence lifetime can be attributed mainly to the change of the excitonic effective volume and the overlap integral as well.

PRESSURE-DEPENDENCE OF PHOTOLUMINESCENCE FROM ZNSE-TE-(CDSE)(1) (ZNSE)(3) SUPERLATTICE QUANTUM-WELLS

Pressure dependence of photoluminescence from ZnSe:Te-(CdSe)(1)(ZnSe)(3) short period superlattice quantum wells is reported. In addition to the exciton band from the superlattice layers, strong bands for localized excitons self-trapped al single Te (Te-1) atom, double Te atoms (Te-2) and Te clusters (Te-n, n greater than or equal to 3) as well as for the free excitons in isoelectronic Te incorporated ZnSe layers are observed. Significant differences in the pressure and temperature dependencies of the observed exciton transitions are presented and discussed.

SOI CMOS模拟集成电路发展概述

从SOI CMOS模拟集成电路(IC)中存在的关键问题--浮体效应--及其影响出发,介绍了在解决浮体效应以后,已实现的有代表性的模拟集成电路的发展状况.特别指出了SOICMOS在实现RF电路及SOC芯片中的优点.

6H－SiC MOS结构电特性及其辐照效应的研究

对SiC MOS结构辐照引起的电参数退化及其电特性进行了研究。结果说明

气态源分子束外延GeSi合金中的低温生长动力学研究

用气态源分子束外延(GSMBE)法研究了Ge_xSi_(1-x)合金的低温(≤500℃)生长动力学问题，所使用的源分别是乙硅烷和固态锗。在恒定的乙硅烷流量(4sccm)Ge源炉温度(1200℃)下，合金中的Ge组分x随衬底温度的降低而升高；另一方面，当衬底温度(500℃)和乙硅烷流度升高到一定值以上时，x值不再随Ge源炉温度的升高而增大,而趋向于饱和在0.45附近。基于乙硅烷及H原子在Si原子和Ge原子表面上不同的吸附和脱附过程，定性地解释了上述生长动力学现象。

Single steady frequency and narrow line width external cavity semiconductor laser

A single longitudinal mode and narrow line width external cavity semiconductor laser is proposed. It is constructed with a semiconductor laser, collimator, a flame grating, and current and temperature control systems. The one facet of semiconductor laser is covered by high transmission film, and another is covered by high reflection film. The flame grating is used as light feedback element to select the mode of the semiconductor laser. The temperature of the constructed external cavity semiconductor laser is stabilized in order of 10(-3)degreesC by temperature control system. The experiments have been carried out and the results obtained-the spectral fine width of this laser is compressed to be less than 1.4MHz from its original line-width of more than 1200GHz and the output stability (including power and mode) is remarkably enhanced.

In situ doping of 3C-SiC grown on (0001) sapphire substrates by LPCVD

The heteroepitaxial growth of n-type and p-type 3C-SiC on (0001) sapphire substrates has been performed with a supply of SiH4+C2H4+H-2 system by introducing ammonia (NH3) and diborane (B2H6) precursors, respectively, into gas mixtures. Intentionally incorporated nitrogen impurity levels were affected by changing the Si/C ratio within the growth reactor. As an acceptor, boron can be added uniformly into the growing 3C-SiC epilayers. Nitrogen-doped 3C-SiC epilayers were n-type conduction, and boron-doped epilayers were p-type and probably heavily compensated.

High-quality GaN grown by gas-source MBE

High-quality GaN epilayers were consistently obtained using a home-made gas-sourer MBE system on sapphire substrates. Room-temperature electron mobility of the grown GaN film is 300 cm(2)/V s with a background electron concentration as low as 2 x 10(17) cm(-3) The full-width at half-maximum of the GaN (0 0 0 2) double-crystal X-ray rocking curve is 6 arcmin. At low temperature (3.5 K), the FWHM of the: near-band-edge photoluminescence emission line is 10 meV. Furthermore, using piezoelectric effect alone with the high-quality films, two-dimensional electron gas was formed in a GaN/AlN/GaN/sapphire structure. Its room-temperature and low-temperature (77 K) electron mobility is 680 cm(2)/V s and 1700 cm(2)/V s, and the corresponding sheet electron density is 3.2 x 10(13) and 2.6 x 10(13) cm(-2), respectively. (C) 2001 Published by Elsevier Science.