TEM study of compositional modulations in a GaInAsSb film grown on GaSb vicinal substrates

Quaternary semiconductor alloys based on GaSb are suitable for thermophotovoltaic (TPV) cell applications as they have low and adjustable band-gap. However, they exhibit phase separation which destroys band-gap uniformity. In this work, GaInAsSb thin films grown on GaSb vicinal substrates with different miscut angles were studied by CTEM, in order to determine the influence of the cut-off angle on phase separation. It was found that the coatings exhibit two types of compositional modulation (CM), one parallel (Vertical CM - VCM) and the other forming an angle (Lateral CM - LCM) with the substrate plane. The VCM does not depend on the cut-off angle while the LCM does.