Deep level defects in Ga- and N-polarity GaN grown by molecular beam epitaxy on si(111)

Abstract

Deep level transient spectroscopy has been used to characterize the deep level traps in Ga- and N-polarity GaN films grown by plasma assisted molecular beam epitaxy on Si(111) substrate. The two deep level traps at E-c-E-t similar to 0.21 eV (E-1) and E-c-E-t similar to 0.48 eV (E-2) have been detected in Ga-polarity GaN, The E-1 level commonly observed deep trap related to the nitrogen vacancy in GaN. It is found that, the E-2 level exhibits logarithmic capture kinetic behavior and substantially increases its capture cross section from 10(-15) to 10(-12) cm(2) by employing different pulse width ranging from 5 ms to 35 ms. Such behavior of E-2 trap with filling pulse length attributes that, the trap is originated from threading dislocations. In case of N-polarity GaN, we observed two deep level traps with activation energies of E-c-E-t similar to 0.53 eV (E-3) and E-c-E-t similar to 0.89 eV (E-4). The estimated capture cross-sections (sigma(s)) for these defects were found to be similar to 2.51 x 10(-15) cm(2) and similar to 5.21 x 10(-16) cm(2) respectively. The E-3 and E-4 are nitrogen antisite point defect and extended defect related to dislocation deep levels, results from growth on N-polarity crystal structure. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.