Electromodulation spectra of high-resistance p and n GaAs doped with chromium

From the electromodulation spectra of high-resistance p and n GaAs doped with chromium, the ionization energies of the acceptor levels of chromium are determined. They are $\varepsilon_{1 A V}= 0,61\pm 0,01$ eV and $\varepsilon_{2 A V} = 0,870 \pm 0,005$ eV and are independent of the temperature in the range 80-300K.