Abstract
Semiconductor-semiconductor heterojunctions are attracting much interest in relation to thin-film growth technology, device applications and electcon physics. To obtain fundamental physical understanding about these heterojunctions, we review the nature of extended eletronic states near the interface.
Regarding energy-band discontinuities at the interface, the basic parameters, Harrison's LCAO prediction, and Cohen's self-consistent pseudopotential method are discussed. Also, empirical approaches are surveyed. Among them, a recent C-V experiment seems the most reliable. When the effective-mass theory is applied to heterojunctions, the boundary condition for envelope functions at the interface becomes a specific problem. Ando-Mori's determination by the tight-binding method is detailed. Self-consistent calculation for AlGaAs/GaAs heterojunctions was carried out by Ando and by Stern. The results of the subband structure and the carrier mobility are in good agreement with observed light-scattering spectra and the Hall experiment, respectively.
