A STRUCTURAL AND OPTICAL STUDY OF SPUTTERED INP FILMS AS A FUNCTION OF PREPARATION TEMPERATURE

Approximately stoichiometric InP films have been prepared over a range of substrate temperature T-s. The structure of the deposited films ha s been investigated by means of transmission electron microscopy (TEM) , extended x-ray absorption fine structure (EXAFS) and x-ray photoelec tron spectroscopy (XPS) experiments. TEM measurements reveal that samp les deposited below approximately 100 degrees C are amorphous while fi lms prepared above this temperature are microcrystalline in nature. Bo th EXAFS and XPS measurements indicate that bond angle disorder in the atomic network decreases as T-s is raised. Changes in the optical abs orption properties are observed as T-s is increased, with particularly marked changes noted over the relatively narrow temperature range 110 -150 degrees C; the bandgap E(04) (defined as the photon energy at whi ch the absorption coefficient is equal to 10(4) cm(-1)) increases from 1.1 to 1.25 eV while n(0.5) (the refractive index at 0.5 eV photon en ergy) decreases from 3.7 to 3.3 over the above 40 degrees C temperatur e range. The changes in optical properties are correlated with the str uctural data.