Anelastic relaxation in semi-insulating InP

The elastic energy loss of InP has been measured between 1.9 and 450 K in the frequency range 1 to 16 kHz. In the InP samples displaying the semi-insulating state, obtained either by thermally treating at 950°C the undoped material or by doping with Fe, a well-developed thermally activated relaxation process appears at 300 K. The corresponding peak is described by a single-time Debye curve with an activation energy E=0.67 eV and a pre-exponential factor of the relaxation rate tau 0-1=3× 1014 s-1, indicating the presence of a species mobile at room temperature and constituted by atomic complexes. Instead, in the non-semi-insulating InP sample, the peak at 300 K is either absent or masked by the background. The possibility is discussed that the mechanism giving rise to the relaxation peak is due to hydrogen-related defects.