Structural and optical characterization of undoped and indium-doped US films grown by pulsed laser deposition

Three types of US thin films, one undoped and two n-doped, have been grown on the quartz substrates by pulsed laser deposition technique. The two n-doped films have been deposited by laser ablating a home-made target obtained by mixing US and metallic Indium powders with two different concentrations of In powder weight (1 and 5%). The films were grown highly oriented along the (002) direction of the hexagonal phase. Raman spectra show that the LO peak broadens as the Indium doping increases. due to the increase of compositional disorder. Band filling effects characterize the absorption spectra of the heavily doped films: in particular. the band gap of the doped films presents an evident blue-shift with respect to the undoped film, due to Burstein-Moss effect. Photoluminescence spectra show the intrinsic radiative recombinations persisting up to room temperature. (C) 2003 Elsevier B.V All rights reserved.