Deep trap levels in Mg-doped samples, which had been grown by means of metalorganic vapour phase epitaxy, were studied by using deep level transient spectroscopy. The Mg concentration in the sample was 4.8 x 1019/cm3, but the hole concentration was as low as 1.3 x 1017/cm3 at room temperature. The deep level transient spectrum contained a dominant peak with an activation energy of 0.41eV. This was accompanied by additional peaks with activation energies of 0.49eV and 0.59eV. It was found the dominant peak comprised 5 sub-peaks, each of which had a different activation energy and capture cross-section. Heat treatment of the same samples was used to observe variations in activation energy, capture cross-section, and amplitude of the deep level transient spectroscopy signals. It was found that the longer the heat treatment, the lower was the amplitude of the deep level transient spectroscopy peaks. It was therefore suggested that the decrease in the signal originated from H atoms which out-diffused from the film during annealing. The possible origin of multiple trap levels was explained in terms of Mg-N-H complexes.

Effect of Thermal Annealing on Hole Trap Levels in Mg-Doped GaN Grown by Metalorganic Vapor Phase Epitaxy Q.S.Zhu, H.Nagai, Y.Kawaguchi, K.Hiramatsu, N.Sawaki: Journal of Vacuum Science and Technology A, 2000, 18[1], 261-7