Electronic structures of strained-layer superlattices (Si)2n/(Si1−xGex)2n (100) with n=1–10

Abstract

The empirical tight‐binding method is used to calculate the electronic structures of type II strained‐layer semiconductor superlattices (Si)_2n /(Si_1−x Ge_x )_2n (100) with n=1–10. The effects of lattice‐constant variation on nearest neighbor interactions have been taken into account. The energy gaps and positions of the conduction‐band minimum are obtained for various number of layers. The effects of band folding and band discontinuity on the gap of Si/Ge are analyzed. The 2DEG (two‐dimensional electron gas) localized in the Si layer can be explained in terms of the change of ΔE_c because of structural strain. The strained band agrees quite well with electroreflectance experiment and other calculations. Studies on interface states are also presented.