Growth and Characterization of GaSb Grown from a Split-Sputtering Target

Abstract

GaSb is a semiconductor material having a narrow band gap in the infrared spectrum of 0.72 eV. This research is intended to investigate the low cost growth and properties of GaSb and to propose this material as a candidate for a cost effective method of developing a GaSb /silicon tandem solar cell. This work investigated the sputtering of GaSb films onto a glass substrate from a GaSb/Sb split-sputtering target. A GaSb compound was formed by placing Ga and Sb elements inside a vacuum sealed ampule. The ampule was placed inside a box furnace and heated at 800 0 C successfully forming a GaSb compound. Both GaSb and Sb were molded into a semicircular shape in a quartz container. X-ray diffraction (XRD) was conducted on sputtered films in order to confirm their structure. XRD peaks of the film were compared with reference peaks found on the Inorganic Crystal Structure Database (ICSD). GaSb peaks were apparent at specific sputtering chamber conditions of substrate temperature and source-to-substrate distance. Sputtered GaSb films were then further characterized with the Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Hall Effect measurements. A theoretical thickness of the films was calculated using FTIR measurements to be about 1 μm and 0.35 μm for the films grown on a substrate heated with heater powers of 280 watts and 250 watts respectively. SEM confirmed the sample thicknesses with 20% error. Hall Effect measurements resulted in a high carrier concentration and low free carrier activation energy; 7.545 x1019 cm-3 and 0.1017 eV respectively. These values are attributed to the possible existence of anti-site defects.