形变超晶格Si/Ge的能带结构

用经验的紧束缚方法对短周期的(Si)_n/(Ge)_m形变超晶格的电子态进行了计算。结果表明,由于布里渊区折迭的要求,只有当n+m=10时超晶格才可能产生直接能隙。对周期为n+m=10的超晶格,Γ,N,△处的导带谷间的相对位置对直接能隙的形成具有决定作用,而n的大小与衬底的组分对此有极大影响。(Si)₆/(Ge)₄和(Si)₈/(Ge)₂超晶格在Si_1-xG 关键词：

BAND STRUCTURE OF Si/Ge STRAINED LAYER SUPERLATTICE

The electronic structures of short period (Si)_n/(Ge)_m Strainedlayer superlattices (SLS's) are calculated using empirical tight-binding method. The results indicate that due to the zone-folding, only the SLS's with n+m=10 have the posibility to form direct band gap. For SLS's with n+m=10, the type of energy gap is determined by the relative energies of conduction band valleys at Γ, N, and Δ. However, the Ge layers number and the composition of substrate play an important role. For (Si)₆/(Ge)₄ and (Si)₈/(Ge)₂ SLS's grown on Si_1-xGe_x substrate, direct or quasidirect band gap could be got for the substrate composition 0.4≤x≤1.0 For (Si)₄/(Ge)₆, direct gap could be obtained only for 0.3≤x≤0.6, and in (Si)₂/(Ge)₈ SLS's the gap could not be direct for all substrate composition.