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 Ec−Et∼0.21eV (E1) and Ec−Et∼0.48eV (E2) have been detected in Ga-polarity GaN. The E1 level commonly observed deep trap related to the nitrogen vacancy in GaN. It is found that, the E2 level exhibits logarithmic capture kinetic behavior and substantially increases its capture cross section from 10−15 to 10−12cm2 by employing different pulse width ranging from 5ms to 35ms. Such behavior of E2 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 Ec−Et∼0.53eV (E3) and Ec−Et∼0.89eV (E4). The estimated capture cross-sections (σS) for these defects were found to be ∼2.51×10−15cm2 and ∼5.21×10−16cm2 respectively. The E3 and E4 are nitrogen antisite point defect and extended defect related to dislocation deep levels, results from growth on N-polarity crystal structure.