Composition and strain dependence of band offsets at metamorphic In$_{x}$Ga$_{1-x}$As/In$_{y}$Al$_{1-y}$As heterostructures

摘要

We have studied the In$_{x}$Ga$_{1-x}$As/In$_{y}$Al$_{1-y}$As (001) interfaceusing first-principles ab-initio pseudopotential calculations, focusing on theeffects of alloy composition and strain state on the electronic properties. Inparticular we estimate a valence band offset (VBO) of 0.11 eV (InGaAs higher),including spin-orbit and self-energy corrections, for a strain-compensatedconfiguration with homogenous composition $x=y=0.75$ on a lattice-matchedsubstrate. Unintentional composition fluctuations which are typically limitedto a few percent and different short-range order effects give rise only tosmall variations on the VBO, of the order of 0.1 eV or less, whereasintentional substantial changes in the alloys composition allow to achieve ahigh tunability of band offsets. We predict a VBO varying in a range of about1.1 eV for interfaces between the pure arsenides in different strain states asextreme cases of composition variation atIn$_{x}$Ga$_{1-x}$As/In$_{y}$Al$_{1-y}$As heterostructures.