Growth of InAs quantum dots on GaAsSb for the realization of a quantum dot solar cell

Abstract

The InAs/GaAsSb quantum dot/barrier material system has been identified as a candidate for implementing the quantum dot (QD) solar cell for an Sb content of ∼ 12%. We present results from the growth of this system on GaAs substrates by Molecular Beam Epitaxy (MBE). The results show that the growth of GaAsSb requires special care in order to ensure the highest quality interface and also to maintain the Sb composition. When InAs QDs are grown on the GaAsSb, the role of strain in determining the properties of the QDs is seen to be profound. Results from PL studies show that the sizes of the QDs are controlled by the GaAsSb layer thickness and hence the residual strain at the GaAsSb surface. In addition a change from type I to type II transitions can be affected by this method. The implications of these results plus the influence of the substrate choice, and so the strain, on the system properties will be discussed in terms of a QD solar cell design with a strain balanced design enabling a much larger active region and hence higher absorption.