Mechanism for spatial separation of charge carriers in inhomogeneous semiconductor alloys

A novel mechanism is proposed for charge-carrier separation by band-edge steps in inhomogeneous alloys with sufficiently strong compositional fluctuations. The phenomenon is predicted to occur for alloy compositions where the highest valence band and the lowest conduction band have slopes of the same sign as a function of the average alloy composition. We discuss experimental data for indirect-gap $\mathrm{Ga}{\mathrm{As}}_{1-x}{\mathrm{P}}_x$ which provide confirmation of this prediction. Finally, other alloy systems and alloy structures for which related phenomena may occur are suggested.