Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy

Abstract

Deep levels in Mg-doped GaN grown by metal organic chemical vapor deposition (MOCVD), undoped GaN grown by MOCVD, and halide vapor phase epitaxy (HVPE)-grown GaN have been studied using deep level transient spectroscopy and minority charge carrier transient spectroscopy on Schottky diodes. One hole trap, labeled HT1, was detected in the Mg-doped sample. It is observed that the hole emission rate of the trap is enhanced by increasing electric field. By fitting four different theoretical models for field-assisted carrier emission processes, the three-dimensional Coulombic Poole-Frenkel (PF) effect, three-dimensional square well PF effect, phonon-assisted tunneling, and one-dimensional Coulombic PF effect including phonon-assisted tunneling, it is found that the one-dimensional Coulombic PF model, including phonon-assisted tunneling, is consistent with the experimental data. Since the trap exhibits the PF effect, we suggest it is acceptorlike. From the theoretical model, the zero field ionization energy of the trap and an estimate of the hole capture cross section have been determined. Depending on whether the charge state is \ensuremath{-}1 or \ensuremath{-}2 after hole emission, the zero field activation energy ${E}_{i0}$ is 0.57 eV or 0.60 eV, respectively, and the hole capture cross section ${\ensuremath{\sigma}}_{p}$ is $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}$ or $1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}$, respectively. Since the level was not observed in undoped GaN, it is suggested that the trap is associated with an Mg related defect.