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本文讨论了SU(N.M)的空间对称性和布里渊区经折叠后的特殊性质。使用分区变分法计算了超薄层超晶格(GaAs)_n/(AlAs)_n(n=1,2,3)的能带,运用四个势场调整参数所算出的能带和实验结果基本相符。结果表明,(GaAs)_1—(AlAs)_1为间接能隙半导体,禁带宽度为1.87eV,导带底位于Z_x点(1,0,0)(2π/a)。而(GaAs)_n—(AlAs)(n≥2)则为直接能隙半导体,且禁带宽度E_g随着n的增大而减小。并将计算结果和别的理论结果、实验数据作了比较和分析。
This article discusses the spatial symmetry of SU (N.M) and the special properties of the Brillouin region after folding. The energy bands of ultra-thin layer superlattice (GaAs) _n / (AlAs) _n (n = 1,2,3) were calculated using the zonal variation method. The energy bands calculated from the four potential field adjustment parameters and the experimental results Basic match. The results show that (GaAs) _1- (AlAs) _1 is an indirect bandgap semiconductor with a forbidden band width of 1.87eV and a conduction band base of (1, 0,0) (2π / a) at the Z_x point. However, (GaAs) _n- (AlAs) (n≥2) is a direct gap semiconductor, and the band gap E_g decreases with the increase of n. And the calculation results and other theoretical results, experimental data were compared and analyzed.