Low temperature photoluminescence and photoacoustic characterization of Zn-doped InxGa1−xAsySb1−y epitaxial layers for photovoltaic applications

In this paper we present results on the characterization of Zn-doped InGaAsSb epitaxial layers to be used in the development of stacked solar cells. Using the liquid phase epitaxy technique we have grown p-type InGaAsSb layers, using Zn as the dopant, and n-type Te-doped GaSb wafers as substrates. A series of Zn-doped InGaAsSb samples were prepared by changing the amount of Zn in the melt in the range: 0.1–0.9 mg to obtain different p-type doping levels, and consequently, different p–n region characteristics. Low temperature photoluminescence spectra (PL) were measured at 15 K using at various excitation powers in the range 80–160 mW. PL spectra show the presence of an exciton-related band emission around 0.642 eV and a band at 0.633 eV which we have related to radiative emission involving Zn-acceptors. Using the photoacoustic technique we measured the interface recombination velocities related to the interface crystalline quality, showing that the layer–substrate interface quality degrades as the Zn concentration in the layers increases.