Effect of high temperature rapid thermal annealing on optical properties of InGaAsP grown by molecular beam epitaxy

Abstract

The effect of rapid thermal annealing (RTA) on the optical properties of InGaAsP with band-gap energy of around 1.05 eV for quadruple-junction solar cells grown by molecular beam epitaxy (MBE) has been investigated. The photoluminescence (PL) spectrum of InGaAsP film annealed at 800 °C has strong integrated intensity and low activation energy of band-tail states. The time-resolved PL measurement shows that the decay time of the InGaAsP annealed at 800 °C and as-grown one are 11.6 ns and 3.0 ns at 10 K, respectively. An S-shape PL decay time as a function of temperature for the InGaAsP annealed at 800 °C is observed and is explained by the carrier relaxation dynamics. The RTA process induces reorganization of In and Ga inside the alloy due to the existence of miscibility gap in InGaAsP grown by MBE owing to the Be diffusion at high temperature and results in an increased composition uniformity and an improved PL intensity.