Reducing threading dislocation density in GaSb photovoltaic devices on GaAs by using AlSb dislocation filtering layers

Abstract

GaSb based photovoltaic devices have been demonstrated on GaAs substrates by inducing interfacial array of 90° misfit dislocations. Despite the beneficial qualities of the highly stable 90° misfit dislocation, there is a significant density of residual threading dislocations in the GaSb layer, resulting in the degradation of the electrical performance of such photovoltaic cells compared to lattice matched devices. We aim to reduce threading dislocation density by optimizing growth temperature and by using an AlSb dislocation filtering layer. The growth temperature optimization results in a reduction of the threading dislocation density to 1.3 × 108 cm−2. Adding an AlSb dislocation filtering layer further improves the electrical performance of the GaSb solar cells by reducing the threading dislocation density to 4 × 107 cm−2. A comparison between the experimental data and theoretical calculation confirms that the recombination in dislocation centers is a dominant loss mechanism in GaSb solar cell grown on GaAs substrate.