ELECTRONIC-STRUCTURES AND OPTICAL-PROPERTIES OF (GAP)N(ALP)N SHORT-PERIOD SUPERLATTICES WITH N=1 TO 6

In this study we have investigated the origin of the strong intensity of photoluminescence in the short-period superlattices consisting of a pair of indirect-gap semiconductors GaP and AlP. For this purpose we first calculated the electronic structures and optical properties of (GaP)(n)(AlP)(n) short-period superlattices with the clean (001) interface by the norm-conserving pseudopotential method within the local density approximation. In this calculation we showed that the clean-interface (GaP)(n)(AIP)(n) with n=1 and 2 are indirect-gap semiconductors while those with n=3 to 6 are pseudo-direct-gap semiconductors. Although the calculated layer-thickness dependence of band-gap energies is consistent with experimental results, the calculated transition strengths are one to two orders of magnitude smaller than the observed ones. In order to solve this discrepancy, we considered four models of disordering at the interface and investigated the effects of disordering on photoluminescence phenomena. Among the four models, it was shown that the alloying- and ordered-interface models are favorable for transition energies, while the antisite-interface model is favorable for transition strength.