Photo-EPR of defects in undoped semiinsulating GaAs

Electron paramagnetic resonance spectra of as-grown, semi-insulating LEC GaAs at 9 GHz and 35 GHz have revealed three high intensity signals presumably associated with acceptor type defects. The resonances appear only after optical excitation thus confirming that they originate from electrically active centers. The spectral dependence of their photoexcitation has been measured. A comparison with the photo-response of the As sub Ga antisite defect indicates a charge exchange between the As sub Ga donor and at least two of the acceptor type defects. (IAF)