Type-I to type-II superlattice transition in strained layers of InxGa1−xAs grown on InP

Abstract

Optical and electronic properties of ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As strained-layer superlattices grown on InP have been investigated over the entire range of indium compositions, 0<x<1. We demonstrate a type-I to type-II superlattice transition at x≲0.20. Below this critical concentration electrons become confined to the InP layer. Excellent agreement is obtained with a band-structure calculation based on empirical relative valence-band energies and deformation-potential theory. This agreement suggessts that the effect of strain on these relative energies can be neglected.