High field magneto-optical study of the band structure of GaAsAlGaAs and GaAsAlAs short period superlattices

Abstract

Magneto-absorption and magneto-luminescince spectra in (GaAs) m /(Al x Ga 1−xAs) n (type I) and (GaAs) m /(AlAs) n (type II) short period superlattices were measured in pulsed high magnetic fields up to 40T applied both parallel (B |) and perpendicular (B ⊥) to the layers. Well- defined oscillatory structures were observed in type I samples with ( m, n)=(6,6) and (7,5) for both field directions. For B |, the Landau level energies were calculated for both the conduction and valence band on the basis of the Kronig-Penny model, and excellent agreement was obtained with the experimental data. This result shows that the effective mass approximation is still adequate for these ( m, n). In type II samples with ( m, n)=(3,5) and (5,6), weak oscillations were observed only for B ⊥. A very large anisotropy was observed in magneto-luminescence spectra, showing that the lowest conduction band is of the X z character.