Using deep-level transient spectroscopy, we have studied the electrical properties of defects introduced in epitaxially grown n-GaN during 2-MeV proton bombardment. The main defects detected, ER2 and ER3, are introduced at rates of 400±150 and 600±100 cm−1, respectively, and have energy levels at 0.16±0.03 and 0.20±0.01 eV, respectively, below the conduction band. A less prominent defect, ER1, with an energy level at 0.13±0.01 eV below the conduction band, is introduced at a rate of 30±10 cm−1. The small capture cross section of ER3 [(8±4)×10−18 cm2] implies that it is in a neutral or negative state when above the Fermi level.

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The boron acceptor in GH-SiC was investigated using electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). The hyperfine interactions with "B could be determined precisely for the two quasicubic and the hexagonal sites. The microscopic model suggested from the EPR and ENDOR results is as follows: boron occupies a silicon site and is a negatively charged ligand to an adjacent carbon atom on which most of the unpaired spin density is located. At low temperatures the symmetry of the two quasi-cubic site defects is monoclinic, while the hexagonal site defect has C, , symmetry about the hexagonal axis. At about 50 K the two quasi-cubic site defects experience a thermally activated motion of the hole at the adjacent carbon about the hexagonal crystal axis and the apparent defect symmetry also becomes C3". The boron acceptor should be regarded as a boron-induced carbon acceptor.

BaFBr is usually contaminated with oxygen which influences the performance of this well known X-ray storage phosphor material. Oxygen is incorporated as a diamagnetic O2- ion on F- sites with a nearby charge-compensating vacancy in the Br- sublattice, as is known from the paramagnetic O-F and F(Br-) centres created by room-temperature X-irradiation and studied in detail with electron paramagnetic resonance (EPR) techniques. It is shown that BaEBr:O2-F has a luminescence band excited at 4.95 eV, peaking at 2.43 eV with two radiative lifetimes of 0.2 ms and 1 ms, respectively. With luminescence-detected EPR (i.e. optically detected magnetic resonance (ODMR)), it is shown that the luminescence is due to an excited triplet state of an O2-F-Br- vacancy pair. Time-resolved ODMR measurements reveal the same radiative lifetimes as seen in luminescence. No singlet emission was observed. The zero-field splitting can be explained assuming a F(Br-)-O-F pair defect as the excited triplet state.

We have used deep level transient spectroscopy to study the electrical properties of defects introduced in epitaxial n-GaN during sputter deposition of Au Schottky contacts. Four defects, located 0.22±0.02, 0.30±0.01, 0.40±0.01, and 0.45±0.10 eV below the conduction band, were characterized. The first of these defects has similar electronic properties as a radiation induced defect in GaN, while the second appears to be the same as a defect in the as-grown material. The latter two defects have not previously been observed in as-grown or processed epitaxial GaN.