In_xGa_(1-x)As/GaAs应变超晶格的电子结构

用有效质量理论研究了[001]和[111]方向生长的In_xGa_(1-x)As/GaAs应变超晶格的电子结构.具体计算了价带能级的色散曲线和光吸收曲线.沿[001]方向生长的光吸收曲线与实验进行了比较.内应变使重轻空穴能级发生上升和下降.由于压电效应,[111]方向生长的超晶格应变层内存在很强的内电场(1.5×10~5V/cm),而对[001]方向生长的应变超晶格不产生内电场.     

FIRST-PRINCIPLE SELF-CONSISTENT PSEUDOPOTENTIAL CALCULATION OF THE ELECTRONIC STRUCTURES OF SHORT-PERIOD (GaAs)m(AlAs)n SUPERLATT1CES

With the local density approximation, the band structares of the short-period (GaAs)₁(AlAs)₁ and (GaAs)₂(AlAs)₁ superlattices are calculated by using the first-principle self-consistent pseudopotential method. The results show that the (GaAs)₁(AlAs)₁ superlattice is an indirect semiconductor, and the lowest conduction band state is at point R in the Brillouin zone; the (GaAs)₂(AlAs)₁ superlattice is a direct semiconductor and the lowest conduction band state is at point Γ. The squared matrix elements of transition are calculated. The pressure coefficients of energy gaps of the (GaAs)₁(AlAs)₁ and (GaAs)₂(AlAs)₁ superlattices are calculated and compared with those obtained by hydrostatic pressure experiments.     

电场下超晶格GaAs/Ga_(1-x)Al_xAs[111]的电子结构

用有效质量理论研究了GaAs/Ga_(1-x) Al_xAs[111]超晶格在外加电场下的电子结构.具体计算了超晶格的子能带色散关系曲线,子能级随外加电场的变化,并且计算了k_u=0的光跃迁矩阵元平方随电场的变化.与零电场情况相比,发现在k_u≠0处子能带的二重简并解除.随电场的增大,△n=0的跃迁减小,而△n≠0的跃迁增大.考虑单轴压力效应后,轻空穴和重空穴的能级位置发生下降和上升.     

FIRST-PRINCIPLE SELF-CONSISTENT PSEUDOPOTENTIAL CALCULATION OF THE ELECTRONIC STRUCTURES OF SHORT-PERIOD (GaAs)m(AlAs)n SUPERLATT1CES

With the local density approximation, the band structares of the short-period (GaAs)₁(AlAs)₁ and (GaAs)₂(AlAs)₁ superlattices are calculated by using the first-principle self-consistent pseudopotential method. The results show that the (GaAs)₁(AlAs)₁ superlattice is an indirect semiconductor, and the lowest conduction band state is at point R in the Brillouin zone; the (GaAs)₂(AlAs)₁ superlattice is a direct semiconductor and the lowest conduction band state is at point Γ. The squared matrix elements of transition are calculated. The pressure coefficients of energy gaps of the (GaAs)₁(AlAs)₁ and (GaAs)₂(AlAs)₁ superlattices are calculated and compared with those obtained by hydrostatic pressure experiments.     

GaAs／Al0.4Ga0.6As多量了阱红外探测器光吸收计算

本文在有效质量理论基础上计算了ＧａＡｓ／Ａｌ０．４Ｇａ０．６Ａｓ多量了阱子带间光吸收谱以及电子态密度，具体讨论了两种情况的吸收，第一种情况是量子阱只存在一个基态；第二种情况是量子阱中存在一个基态同时还存在一个激发态，最后与有关实验进行比较。     

T—H模型临界面的确定和相变研究

运用实空间重整化群得到了六角格子上T-H模型的相变流图、非平凡不动点、热指数等。用平均场自洽方程组确定了T-H模型的一级相变、二级相变临界面及三临界点。由r-△变换严格给出了T-H模型的临界面和部分临界指数。 关键词：     

天津市某电子厂房净化空调工程改造设计

本文在天津某电子厂房原有的净化空调工程基础上，对工艺布置和净化空调系统提出改造方案，并对方案设计进行了简单的介绍。     

GaAs／Al_（0．4）Ga_（0．6）As多量子阱红外探测器光吸收计算

本文在有效质量理论基础上计算了ＧａＡｓ／Ａｌ０．４Ｇａ０．６Ａｓ多量子阱子带间光吸收谱以及电子态密度。具体讨论了两种情况的吸收．第一种情况是量子阱中只存在一个基态；第二种情况是量子阱中存在一个基态同时还存在一个激发态．最后与有关实验进行比较．     

短周期(Ge)_n(Si)_n应变超晶格电子结构的自洽赝势计算

在局域密度近似下,用第一原理自洽赝势的方法计算了短周期超晶格(Ge)_1(Si)_1和(Ge)_2(Si)_2的能带结构。结果表明(Ge)_1(Si)_1是间接带,导带最低点在布里渊区的X点。(Ge)_2(Si)_2也是间接带,导带最低点在布里渊区M点附近。给出了禁带宽度及自旋轨道分裂值,并与有关的理论和实验做了比较。