IDENTITY OF THE CONDUCTION-BAND MINIMUM IN [ALAS](1)/[GAAS](1) (001) SUPERLATTICES - INTERMIXING-INDUCED REVERSAL OF STATES

First-principles pseudopotential calculations on the (001) (AlAs)1/(GaAs)1 superlattice (SL) shows that partial intermixing of the A and Ga atoms relative to the abrupt case lowers its formation energy, making this SL even stabler at low T than the fully randomized Al0.5Ga0.5sAs alloy. Concomitantly, the conduction-band minimum (CBM) reverts from the GaAs L-derived state, to the X(xy)-derived AlAs state. The Previously noted discrepancy between theory (pertinent to abrupt SL's and yielding an L-derived CBM) and experiment (yielding an X(xy)-derived CBM) is therefore attributed to insufficient interfacial abruptness in the samples used to date in experimental studies.