An approach was presented which permitted the analysis of grown-in defects in n-type samples grown by metalorganic vapor phase epitaxy. It related the presence of various structural defects to the concentrations and properties of distinct deep levels. Transmission electron microscopy and electron beam-induced current microscopy, together with post-growth hydrogenation, were used to determine the threading dislocation densities and to observe the local electrical activity. Deep-level optical and transient spectroscopy were also used to detect deep levels, determine their concentrations and analyze their carrier trapping kinetics. A comparison of electron beam-induced current analyses with trap spectra, before and after hydrogenation, established a strong correlation: between levels at Ec - Et = 0.58 and 1.35eV, and recombination centers distributed in the field of the GaN films. Electron beam-induced current analysis showed that, regardless of hydrogenation, threading dislocations behaved as strong recombination centers. This indicated that there must be a deep level which was associated with these regions. A level which was observed at Ec - 2.64/Ev + 0.87eV was a good candidate, with which to account for the electrical activity of the threading dislocations, because it captured both electrons and holes in a manner which was characteristic of recombination centers. This was supported by deep-level transient spectroscopic analyses, of the trapping kinetics for this level, that revealed a behavior which was characteristic of a linear arrangement of point defects along the threading dislocations.

Carrier Trapping and Recombination at Point Defects and Dislocations in MOCVD n-GaN. A.Hierro, M.Hansen, L.Zhao, J.S.Speck, U.K.Mishra, S.P.DenBaars, S.A.Ringel: Physica Status Solidi B, 2001, 228[3], 937-46