Investigation of the absorption ofCr2+(3d4)in GaAs

Abstract

Results on the absorption of intracenter transitions of the ${\mathrm{Cr}}^{2+}$ impurity charge state ($3d^4$) in GaAs are reported for different samples with various free carrier and chromium concentrations. The analysis of the data gives limiting values for the Jahn-Teller energies in the ground and excited states of the ${\mathrm{Cr}}^{2+}$ impurity. The strengths of these couplings are discussed with different models. The effect of the hydrostatic pressure up to 10 kbars at 300 and 77 K is also reported and it is shown that, in specific conditions, the ${\mathrm{Cr}}^{1+}\left(3\mathrm{}{d}^5\right)$ state can be activated by the pressure against the ${\mathrm{Cr}}^{2+}$ state. These experiments prove that the ${\mathrm{Cr}}^{1+}$ energy level is above the GaAs conduction band.