Detailed deep trap analysis in Mg-doped p-type GaN layers grown by MOVPE

p-Type Mg-doped GaN layers grown by metal organic vapor phase epitaxy on un doped GaN buffer layers on (0001) sapphire substrates were investigated by thermal admittance spectroscopy, temperature dependence conductivity and th ermally stimulated currents. A detailed trap characterization in the p-type GaN:Mg as well as in the undoped buffer layers shows that the TAS peaks ob served from the p-type samples are caused by Mg-defects. Furthermore, the u ndoped buffer layer mainly dominates the optical induced deep defect-to-ban d transitions as measured by photoelectrical optical admittance spectroscop y. An increasing Mg-doping level introduces an enhancement of a deep defect signal at about E-G-(280-360) meV. These results show the complex nature o f the Mg defect and the introduction of further deep defects by the doping process. (C) 2001 Elsevier Science B.V. All rights reserved.