POOLE-FRENKEL-EFFECT ASSISTED EMISSION FROM DEEP DONOR LEVEL IN CHROMIUM-DOPED GAP

The electrical properties of chromium-related defects in GaP are inves tigated. Using deep-level transient spectroscopy, a related deep level is observed in p-type GaP exhibiting an activation energy, associated with hole emission, of 0.5 eV. Detailed capacitance transient investi gations were undertaken to study the electric field dependence, This e mission rate which is found to have a field dependence can be fitted b y a Poole-Frenkel model. Evidence is given that the trap is the Cr4+/3 + deep donor level in GaP caused by substitutional Cr on Ga sites. Thi s trap seems to be well adapted to compensate donors for the growth of the semi-insulating Gap. (C) 1998 American Institute of Physics.