Electromodulation spectra of high resistance GaAs(O)

The electromodulation spectra of maximally high resistance (MHR) GaAs(O) with a specific dark resistance of 300 K of $\rho \approx 2\cdot 10^9$ $\Omega \cdot см$ are investigated. In this material the deep donor level of oxygen is greatly filled with holes, which makes it possible to examine their photoionization in a valent zone. Resonance peaks of electroabsorption are recorded in the electromodulational spectra which are associated with the particular transitions. The energy of ionization of the donor (D) level of the oxygen is equal to $\epsilon_{Dv}=0.76\pm0.01$ eV and is constant in a range of 80-300 K.