EFFECT OF DEVIATION FROM STOICHIOMETRY AND THERMAL ANNEALING ON AMORPHOUS GALLIUM ANTIMONIDE FILMS

a-Ga1-xSbx films were deposited in a specially designed flash evaporation apparatus. The control of the evaporation parameters allowed us to prepare stoichiometric and Sb-rich samples. The physical properties of the material were analyzed using optical spectroscopy, x-ray diffraction, electrical conductivity, Raman scattering, infrared absorption, electron energy loss, and Auger electron spectroscopies. The dark conductivity of several samples of variable composition was measured. Variable range hopping dominates the transport process for stoichiometric material while in the Sb-richer samples the phonon-assisted hopping between tail states probably dominates. A substantial increase in the electrical conductivity due to chemical disorder is observed when the composition is far from stoichiometry. A sequence of heat treatments of a near-stoichiometric sample showed two qualitatively different effects. At low temperatures, before the onset of crystallization, an ordering of the amorphous matrix is observed. At higher annealing temperatures GaSb and Sb crystallites are formed. The experimental data and current theories suggest that the partially crystallized material is a mixture of stoichiometric GaSb (and eventually Sb) microcrystals embedded in an Sb-rich a-Ga1-xSbx matrix. The effects of disorder produced by the departure from stoichiometry and by partial crystallization were compared. © 1995 The American Physical Society.