An approach was used that allows the analysis of grown-in defects in n-GaN grown by metal organic vapor phase epitaxy by relating the presence of various structural defects to the concentration 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 density and observe their local electrical activity. In conjunction, deep level optical and transient spectroscopies were used to detect deep levels, determine their concentration and analyze their carrier trapping kinetics for these films. The comparison of electron beam induced current analysis with trap spectra prior and after hydrogenation establishes a strong correlation between two specific levels, at Ec - Et = 0.58 and 1.35eV, and recombination centers distributed in the field of the GaN films. Further, electron beam induced current analysis showed that, independent of hydrogenation, threading dislocations behaved as strong recombination centers, and indicated that there must be a deep level associated with these regions. A level observed at Ec - 2.64/Ev + 0.87eV was a good candidate to account for the electrical activity of the threading dislocations because it captures both electrons and holes, which was characteristic of recombination centers. This was supported by deep level transient spectroscopic analysis of the trapping kinetics for this level that reveals a behavior characteristic of a linear arrangement of point defects likely found 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