Preparation and characterization of pulse electrodeposited GaAs films

Abstract

GaAs is a III–V compound possessing high mobility and a direct band gap of 1.43 eV, making it a very suitable candidate for photovoltaic applications. Thin GaAs films were prepared by plating an aqueous solution containing GaCl3 and As2O3 at a pH of 2 and at room temperature. The current density was kept at 50 mA cm–2 and the duty cycle was varied in the range 10–50%. The films were deposited on titanium, nickel and tin oxide coated glass substrates. Films exhibited polycrystalline nature with peaks corresponding to single-phase GaAs. Optical absorption measurements indicated a direct band gap of 1.40 eV. Atomic force microscope measurements indicated uniform coverage with large crystallites for the films deposited at higher duty cycles. Photoelectrochemical cells were made using the films as photoelectrodes and graphite as counter electrode in 1 M polysulphide electrolyte. At 60 mW cm–2 illumination, an open-circuit voltage of 0.5 V and a short-circuit current density of 5.0 mA cm–2 were observed for the films deposited at a duty cycle of 50%. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)