Charge-Transfer Cr3+(3d3)-]Cr2+(3d4) In Chromium-Doped Gaas

Results on the absorption and electron paramagnetic resonance measurements on chromium-doped GaAs are reported. For $p$-type samples the main optical transitions are shown to be due to a photoionization process which has been measured as a function of temperature and hydrostatic pressure. A model, developed in the configurational diagram scheme and using two types of relaxation, is proposed to explain the experimental results.