Band structure of Al/Si/n-type GaAs with a strained Si interfacial layer

The band structure of a coherently strained Si layer (< 15 Angstrom) on GaAs has been calculated using the empirical pseudopotential method. The pseudopotential form factor of the strained Si layer is derived by considering that the pseudopotential of the strained layer is slightly modified by a factor which is proportional to the volume change of the unit cell. The band-structure calculation indicates that the band gap of the strained Si layer is 0.7 eV, which is substantially smaller than that of the bulk Si. A revised band-structure model for Al/Si/n-type GaAs based on the above calculation is proposed, which agrees very well with the experimental results. This model implies that for the coherently strained Si interfacial layer, the Fermi level is unpinned not only at the Si-GaAs interface but also at the Al-Si interface.