Deep levels in n-GaN Doped with Carbon Studied by Deep Level and Minority Carrier Transient Spectroscopies

Electron and hole traps in the carbon doping of n-type GaN films grown by metal-organic chemical vapor deposition were investigated by deep level and minority carrier transient spectroscopies. Four electron traps were observed in the samples. Of these traps, the electron trap concentration of E2 (Ec - 0.40 eV) rose with increasing C incorporation. Two hole traps H1 (Ev + 0.86 eV) and H2 also showed the dependence of C doping concentration. According to these results, traps E2, H1, and H2 correspond to C-related defects. Moreover, the energy level of H1 was consistent with an ionization energy of 0.9 eV of C-N acting as a deep acceptor, which might give rise to conventional yellow luminescence and current collapse of GaN-based high electron mobility transistors (HEMTs). This was confirmed by photoluminescence (PL) spectra that the integrated intensity of yellow luminescence (YL) band was largely dependent on C incorporation. Therefore, we speculated that hole trap H1 might be responsible for a broad YL band in the samples. (C) 2012 The Japan Society of Applied Physics