OPTICAL STUDIES OF VANADIUM IN GALLIUM-PHOSPHIDE

The results of optical absorption, luminescence, luminescence excitation, and temperature-dependent Hall-effect measurements on semi-insulating n-type GaP:V and n-conducting GaP:V are reported. The gallium V**2** plus /V**3** plus acceptor level is found at E//c - 0. 58 eV. Absorptions due to photoionization transitions from and into this level can be identified. The absorption bands due to the transitions **3A//2 yields **3T//1(F) and yields **3T//1(P) of V**3** plus are measured, both absorptions include three zerophonon lines as well as phonon replica. At low temperatures the photoinduced rechargings V**3** plus reversible reaction reversible reaction V**2** plus are investigated and interpreted in terms of the three charge states of V//G//a and the excitation of electrons from the gallium P**4** plus P//4 anti-site centre.