Deep centers in Si-doped n-type layers, which had been grown by means of reactive molecular beam epitaxy, were studied as a function of the growth conditions by using deep-level transient spectroscopy. When Si-doped layers were grown onto a Si-doped n+-type contact layer at 800C, they exhibited a dominant trap, C1, with an activation energy of 0.44eV and a capture cross-section of 1.3 x 10-15cm2. However, samples which were grown at 750C onto an undoped semi-insulating buffer exhibited prominent traps, D1 and E1, with activation energies and capture cross-sections of 0.20eV and 8.4 x 10-17cm2, and 0.21eV and 1.6 x 10-14cm2, respectively. The E1 trap was believed to be related to a N-vacancy defect, since the Arrhenius signature for E1 was very similar to that of the previously reported trap, E, which was produced by 1MeV electron irradiation of GaN when this was prepared using metal-organic chemical-vapor deposition and hydride vapor-phase epitaxy.

Z.Q.Fang, D.C.Look, W.Kim, Z.Fan, A.Botchkarev, H.Morkoç: Applied Physics Letters, 1998, 72[18], 2277-9