Deep-level transient spectroscopy measurements were carried out on GaN/AlGaN/SiC heterostructures prepared by low-pressure metalorganic vapour phase epitaxy. Si-doped n-GaN layers were grown using an n-AlGaN nucleation layer (8% and 30% of aluminium) on two kinds of p-type 4H-SiC substrates. The deep-level transient spectra of on-axis (00•1) grown samples exhibited a dominant peak of a majority carrier trap with apparent activation energy close to 0.80eV and capture cross-section of about 5 x 10−14cm2 regardless of the AlGaN composition. The energy of this deep level decreased with increasing electrical field due to Poole–Frenkel effect. Carrier capture kinetics indicated interacting point defects arranged along a line, probably a threading dislocation. Two additional traps (0.52 and 0.83eV) were found in on-axis samples with 8% AlGaN composition. For 30% Al content, only a 0.83eV level was detected. Majority carrier trap with activation energy of 0.66eV was observed in the off-axis grown samples. This level was probably related to an interface defect or to a defect lying near the heterojunction interface.

Deep Defects in GaN/AlGaN/SiC Heterostructures. D.Kindl, P.Hubík, J.Krištofik, J.J.Mareš, Z.Výborný, M.R.Leys, S.Boeykens: Journal of Applied Physics, 2009, 105[9], 093706