Effect of ordering on the energy spectrum of narrow-gap III-V alloys: Possibility of the transition into the gapless state.

Abstract

The energy spectrum of a narrow-gap ordered alloy is calculated using the three-band Kane model. It is shown that when the energy gap, reduced by ordering, becomes negative, the transition to a gapless, rather than a semimetallic, state occurs. In order to study the effects beyond the Kane model, the exact equation for the energy spectrum including the finite hole mass and the band warp is derived. The stability of a gapless state with respect to these higher-band corrections is demonstrated.