Electrical and optical properties of chromium doped GaP

The electrical properties of p-type GaP:Cr:Zn and n-type GaP:Cr:S samples h ave been studied using Deep Level Transient Spectroscopy (DLTS). In GaP:Cr: Zn a deep hole emitting level is detected with a thermal activation energy of E-v + 0.48 eV and attributed to the Cr3+/4+ donor level of substitutiona l Cr-Ga In GaP:Cr:S a deep electron emitting level is detected at E-c- 0.30 eV and attributed to the Cr+/2+ double acceptor level of Cr-Ga The emissio n rates of both levels are found to be electric field dependent which can b e fitted by a Poole-Frenkel model. Deep Level Optical Spectroscopy (DLOS) m easurements were performed on both levels in the filled as well as in their emptied state. The Frank-Condon shifts were estimated from these measureme nts. The spectral shape of these DLOS spectra is discussed as due to photoi onization transitions.