Early measurements on many bulk III-V alloys showed that the spin-orbit splitting ${\Delta }_0$ at the valence-band maximum (VBM) was universally reduced relative to the average value of the end-point constituents. This led to the assumption, guiding much of the subsequent data analysis, that such alloys universally mix some conduction-band s character into the VBM (‘‘interband coupling’’), suppressing ${\Delta }_0$. Our self-consistent electronic-structure calculations for Ga(As,Sb) show very little s mixing in the VBM and an enhancement of ${\Delta }_0$. Intraband p-p coupling is shown to dominate the changes in ${\Delta }_0$.

• Received 5 October 1988

DOI:https://doi.org/10.1103/PhysRevB.39.6279