Proceedings of the International Society of Magnetic Resonance XHIth Meeting Parti joint 29 th AMPERE - 13 th ISMAR »

For the study of defects in III-V semiconductors an enhancement of sensitivity with respect to the conventional detection of electron paramagnetic and electron-nuclear double resonance (EPR/ENDOR) is necessary, because of low defect concentrations together with broad EPR lines and very small sample volumes as in the case of epitaxial layers. This can be achieved by optical detection of EPR and ENDOR (ODEPR/ODENDOR), which can be performed using optical absorption or luminescence. The first method is based on the measurement of a microwave or radio frequency induced change of the magnetic circular dichroism of the optical absorption (MCDA) and the second method detects the corresponding change of the intensity of the photoluminescence (PL) of a paramagnetic defect. Two examples of ODEPR/ODENDOR investigations in the III-V semiconductors GaAs and GaN are given. The investigations of the arsenic antisite-related related) defects in GaAs were based on the MCDA-detection (MCDAEPR/ENDOR), and the experiments on defects in GaN were performed via the PL-detection (PL-EPR/ENDOR). In GaAs several Asoa-related defects can be measured. Three of them have almost undistinguishable EPR spectra. They can only be discriminated with MCDA and MCDA-ENDOR. The PLEPR/ENDOR investigations on GaN were performed with a high frequency setup working at 72GHz. An enhancement in resolution and sensitivity was observed.