LOW-TEMPERATURE PHOTOLUMINESCENCE OF DISORDERED THIN-LAYER GAAS ALAS SUPERLATTICES - EXPERIMENT/

Low-temperature photoluminescence spectra for various disordered thin- layer (GaAs)(m)(AlAs)(n) superlattices have been experimentally studie d. The samples were grown by molecular-beam expitaxy (MBE) growth, and disorder was introduced by varying the thickness of GaAs and AlAs lay ers in the growth direction in various specific but randomly generated sequences. The photoluminescence from disordered superlattice samples shows a strong disorder sequence dependence. Disordered (GaAs)(m)(AlA s)(n) superlattices with m,n distributed in a range of 1-6 shows mainl y a sharp peak at the high-energy side and a broad peak at the low-ene rgy side. According to the study of the temperature, excitation-intens ity, and disorder-sequence dependence of the photoluminescence, the sh arp peak is assigned to bound-exciton recombination and the broad peak to the recombination of electron-hole pairs localized by a disorder p otential induced by layer thickness disorder. Samples with m,n larger than 6 exhibit multiple peaks of similar recombination mechanism. In a ddition, the results demonstrate that the luminescence intensity of di sordered superlattices at T=10 K can be increased by up to two orders of magnitude over that of ordered short-period superlattices.