MIXING OF SUBBANDS IN GAAS ALAS SUPERLATTICES WITH RANDOMLY DISTRIBUTED LAYER THICKNESSES/

The hole subband structure of GaAs/AlAs superlattices with randomly di stributed layer thicknesses is studied with the Luttinger-Kohn Hamilto nian in the Wannier-Bloch mixing representation. By use of Dean's meth od, the eigenvalues and the subband structure of holes are calculated for several samples with various distributions of the random layer thi cknesses. From these results, it is seen that the strong mixing of the hole subbands results in large nonparabolicities in the hole subbands . With an increasing degree of randomness, the effect becomes more and more apparent. It is also found that the introduction of the randomne ss in the layer thicknesses gives rise to a reduction of the energy ga ps and the differences between the hole subbands, and an increase of t he total widths of the hole minibands. The effect of the mixing on the optical properties is also qualitatively discussed.