MOCVD Growth of Doped GaAs/AlGaAs Quantum Heterostructures

The influences of growth techniques of AP-MOCVD GaAs/AlGaAs silicon-doped multi-quantum wells(MQWs), heterostructure bipolar transistors (HBTs), double barrier resonant tunneling diodes(DBRTDs) ontheir structures and performances were studied. Continuously grown MQWs, that is, no growth interruption atthe heterointerfaces, shown blue-shifted, narrower and stronger photoluminescence(PL) compared withinterruptedly grown ones.TEM examination of the interrupted interfaces revealed a bright line correspondingto the compositional fluctuation and impurity adsorption, and indicated noncommutative structures ofAlGaAs/GaAs and GaAs/AlGaAs interfaces. High performance HBTs and DBRTDs were obtained bycontinuously grown method while growth interruption caused performance degradation. It was concluded thatgrowth interruption may cause accumulation of residua1 impurities in the ambient as well as compositionalfluctuation while continuous growth at very low growth rates can overcome such problems.     

MOCVD制备GaAs/AlGaAs异质结和异质结双极晶体管(HBT)的研究

本文应用MOCVD技术制备出高质量的GaAs,AlGaAs外延材料以及GaAs/AlGaAs异质结和多量子阱结构.首次成功地用该技术生长了微波HBT全结构材料,并获得了较高性能的器件结果:300K时直流增益(β)为15～40,77K时为60,截止频率大于10GHz,最高振荡频率为5.5GHz.     

GaAs/AlGaAs多量子阱结构中的电子干涉

由电子波干涉的观点出发,理论分析指出:多量子阱结构势垒以上的电子存在一些分立的弱干涉非定域态.通过红外光激发,量子阱中基态电子可以跃迁到这些态上形成一些吸收峰.理论计算出的吸收峰位置与实验测量到的结果相当一致,并且理论估计的吸收峰强弱也与实验结果一致.     

兰姆激光半经典理论单模解的改进

本文从兰姆激光半经典理论中慢变复振幅极化强度一阶导数项不应忽略为出发点,对此理论做出了改进,得出了单模运转情况下新的激光自洽工作方程,并研究了反转粒子数变化以及极化场变化对场振幅与场位相的影响,以及反转阈值条件,牵引效应与排斥效应等。从而肯定兰姆理论中有关动态运转的理论与图示是错误的。笔者还发现当取腔模振荡频率等于二能级原子共振频率时,极化强度一     

兰姆激光半经典理论多模解的改进

本文在单模解的改进的基础上,考虑电场与极化场互为源,在慢变振幅近似下场强度振幅与极化强度复振幅随时间变化的导数应同时保留。得出了多模运转情况下新的激光自洽工作方程,同时研究了反转粒子数变化以及极化场变化对场振幅与场位相的影响,并导出了双模运转激光器的动态模式。     

束流调制器物理机制与电子学设计

兰州重离子回旋加速器装置H IRFL在某种工作模式下,需要对束流在时间上进行调制,以避免束流对输运线造成损伤;并在加速器引出的束流能量较高且流强很大时,采用束流调制器可使调束在较低的流强下进行,而不必改变加速器的参数。调制器由加装在束运管道上的两个平行电极与相应的电子学电路组成。为满足调制脉冲前后沿的时间要求,电子学设计着重考虑展宽电压放大器频带低品质因数电路设计。     

Chemical Thermodynamic Analysis of Silicon Doping in MOCVD of GaAs System

With chemical thermodynamic method,enthalpies,entropies and heat capacities of(SiH_3)_nAsH_(3-n)(1≤n≤3),(CH_3)_mSiH_(4-m)(1≤m≤4)and their radicals were calculated.Homogeneous reactions equilibrium of 65gas phase species in SiH_4(or Si_2H_6)doped MOCVD GaAs by TMG and AsH_3 system was analyzed,the re-lations of gas phase partial pressures with growth temperatures and input partial pressures were calculated.When the gas phase is saturated with a GaAs:Si solid,the gas phase partial pressures and solid phase siliconimpurity(Si_(Ga)-As,Ga-Si_(As),Si_(Ga)-Si_(As))concentrations were calculated under different growth temperatures andinput partial pressures.With the above results,some of the Si doping behavior in MOCVD of GaAs are ex-plained.     

相干超反斯托克斯喇曼效应(CHARS)产生机理

我们设计了一种取代受激超喇曼效应,产生相干超喇曼光谱的实验方法。即用两束频率分别为ω_1、ω_O的激光束入射到某种介质上,产生频率为ω_3=3ω_1-ω_2的非线性多光子散射效应,称之为相干超反斯托克斯喇曼散射效应。这是一种四阶非线性过程,它要求所测材料为非中心对称,当入射光频率满足与材料共振能级频率ω_(ab)的一定关系时,即满足:ω_(ab)=3ω_1,或ω_(ab)=2ω_1-ω_2,或ω_(ab)=ω_1-ω_2,或ω_(ab)=2ω_1,会产生频率为ω_3=3ω_1-ω_2的共振光谱。     

晶体和频效应非共线匹配理论推导

分析了晶体非共线匹配和频效应的特点,利用晶体中折射率曲面的特点和位相匹配条件,研究了一般情况下参加和频的二束基波与二次谐波的空间传播关系,推导了正负单轴晶体和频各种匹配条件计算公式。还给出了各种特殊情况的匹配公式,最后给出了一匹配曲面的计算结果。