Photoionization transition Cr 3 + → Cr 2 + in GaAs : Cr

2014 The photoionization absorption spectrum of the strongly Cr-doped GaAs samples was measured in the energy region 5 500-11 000 cm-1 under hydrostatic pressure up to 9 kbar at 300 K and 77 K. The EPR measurements with 1.09 03BCm laser excitation shows that this absorption is due to the charge transfer Cr3+ ~ Cr2+ transitions. The theoretical model which takes into account the lattice relaxation effect is used to fit the photoionization absorption curves. The values of optical ionisation energy EO, thermal ionization energy ET and their pressure dependence are obtained. The relaxation energy ER = EO ET is found as about 0.17 eV and the absorption cross section as about 5 x 10-17 cm2. Revue Phys. Appl. 15 (1980) 697-699 MARS 1980, 1 Classification Phy,sics Ahstract,s 71.55 76.30F 78.50