EPR ofCr2+(3d4) in gallium arsenide: Jahn-Teller distortion and photoinduced charge conversion

The spin-Hamiltonian parameters and low-temperature behavior of ${\mathrm{Cr}}^{2+}$ in GaAs are found to correspond closely to those in II-VI zinc-blende compounds, suggesting the occurrence of a static Jahn-Teller distortion. Observation of photoinduced charge conversion among ${\mathrm{Cr}}^{2+}$, ${\mathrm{Cr}}^{3+}$, and ${\mathrm{Cr}}^{1+}$, each possessing a different local symmetry, offers independent evidence that the lowered symmetries at the ${\mathrm{Cr}}^{2+}$ and ${\mathrm{Cr}}^{3+}$ sites are Jahn-Teller generated.