Low-temperature LPE growth and characterization of GaAsSb layers for photovoltaic applications

Abstract

In this paper, we present an original study on metamorphic GaAsSb layers grown by liquid phase epitaxy (LPE) on GaAs substrates for photovoltaic applications. To ensure a controlled growth of the layers with reproducible composition and properties a low-temperature (below 600 °C) variant of LPE was used combined with a precise choice of the technological conditions. This allowed obtaining layers with ∼8% Sb in the As sublattice. The crystal structure, composition, surface morphology, local arrangement and chemical bonding of Sb in the obtained layers were investigated by a variety of measurement methods including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Hall-effect measurements were performed in the temperature range of 80–300 K to clarify the influence of defects on the transport properties. Temperature-dependent photoluminescence spectra at low excitation power were measured to evaluate the optical quality and identify localized states in the grown layers. The optical absorption properties and the transport of the photogenerated carriers in the grown samples were investigated using surface photovoltage (SPV) spectroscopy at room temperature. The SPV measurements have shown that the long-wavelength photosensitivity of the GaAsSb layers is extended down to 1.2 eV.