Magnetic resonance studies of high-resistivity GaN films grown on Al2O3

We have made an attempt to obtain electronic and atomic structure information on the residual defects that exist in high-resitivity GaN epitaxial layers from optically-detected magnetic resonance (ODMR) experiments performed on the broad 3.0 and 2.2 eV photoluminescence (PL) bands observed from these films. The first observation of magnetic resonance on this 3.0 eV band reveals two ODMR signals. The first resonance is sharp (FWHM similar to 3.5 mT) with g similar to 1.950 and is assigned to effective-mass (EM) donors based on previous studies. The second feature is much broader (FWHM similar to 18 mT) with a donor-like g-value of similar to 1.977. This new resonance may be associated with partially EM-like donor states located similar to 54 - 57 meV below the conduction band edge proposed recently to be involved in this 3.0 eV PL band.