OPTICAL-PROPERTIES OF GAAS/ALAS SUPERLATTICES WITH RANDOMLY DISTRIBUTED LAYER THICKNESSES

Electronic states and optical properties of GaAs/AlAs superlattices with randomly distributed layer thicknesses are studied within the framework of the effective-mass approximation in the Wannier-Bloch mixing representation. By use of the improved Dean method, the energy spectra and envelope functions of the carriers in conduction and valence minibands are calculated for several samples with various degrees of randomness. From these results the optical-absorption coefficients of the transitions associated with several valence and conduction minibands are calculated as functions of the photon energy. It is found that the introduction of the randomness in the layer thicknesses gives rise to the reduction of the energy gaps. The calculated absorption edges shift to the infrared side and the intensities of several peaks in the absorption spectrum decrease.