Infrared reflectivity measurements on bulk and epitaxial GaSb. (Carrier concentration and mobility measurements)

Reflectivity measurements have been made on bulk p- and n-type GaSb at 300K and 77K. The results have been analysed to obtain values of carrier concentration and mobility and compared with Hall measurements. Since carrier concentration measurements on n-type GaSb are complicated by the occupation of the satellite L 1c minima, the Hall and reflectivity measurements have been analysed using two-carrier models and compared in terms of total carrier concentration. Good agreement was obtained between the two types of measurement. Calibration curves relating carrier concentration to plasma frequency have been obtained for 300K and 77K and the measurements were consistent with a small positive temperature coefficient for the energy gap between the Gamma 1c and L 1c minima. The reflectivity technique and calibration curves have been used to assess n-type Te-doped epitaxial layers of GaSb. Te concentrations of approximately 10 -6 at.% produced layers with n approximately 5*10 16 cm -3 , the total carrier concentration tending to saturate at approximately 10 19 cm -3 for Te concentrations of approximately 10 -3 at.%.