Miniband spectra of (AlAs)M(GaAs)N(111) superlattices

Electron states in the conduction band of (111)-oriented (AlAs)(M)(GaAs)(N) superlattices (SLs) with M greater than or equal to N and N < 10 are considered. The properties of such SLs are mainly governed by the X-valley electrons in AlAs and the L-valley electrons in GaAs. The calculations are carried out using a previously developed model for the envelope-function matching at heterointerfaces. Miniband spectra, symmetry, and localization of the wave functions, as well as the probabilities of interminiband infrared absorption, are calculated and analyzed. It is shown that the absorption probabilities may be high not only for a light wave polarized along the SL axis, but also for a light wave incident normally to the surface of the structure. It is found that, for analysis of infrared absorption, it is important to take into account the contribution to the wave functions from X-5 valence-band states. (C) 2002 MAIK "Nauka / Interperiodica".