On the nitrogen vacancy in GaN

Abstract

The dominant electrically active defect produced by 0.42 MeV electron irradiation in GaN is a 70 meV donor. Since only N-sublattice displacements can be produced at this energy, and since theory predicts that the N interstitial is a deep acceptor in n-type GaN, we argue that the 70 meV donor is most likely the isolated N vacancy. The background shallow donors, in the 24–26 meV range, actually decrease in concentration, probably due to interactions with mobile N interstitials that are produced by the irradiation. Thus, the recent assignment of a photoluminescence (PL) line as an exciton bound to a 25 meV N-vacancy donor is incompatible with our results. Moreover, we do not observe that PL line in our sample.

Introduction and recovery of Ga and N sublattice defects in electron-irradiated GaN

“…Acceptor-type defects were also observed to be introduced in the irradiation in Ref. 2, but with half the introduction rate of the donors. Our data are in good agreement with this observation, as such low a concentration of additional negatively charged defects would not be observed due to the higher concentrations of both irradiationinduced neutral N vacancies and the in-grown negatively charged Ga vacancies.…”

“…The slight decrease of the average lifetime with increasing temperature can be attributed to initial negatively charged Ga vacancies present in the material already before the irradiation. 2 The introduction rate of 70 meV donors in 0.42 MeV electron irradiation has been observed to be only 0.02 cm −1 . 2 These donors were attributed to the isolated N vacancies.…”

“…However, only in the most recent studies 2,3,7 could the measurements be performed in samples with both low impurity content and low dislocation densities, [9][10][11] allowing more accurate observations of the isolated intrinsic point defects. In most of these studies, the irradiations were performed with electrons of 2 MeV ͑or higher͒ energy, in which case damage is created in both Ga and N sublattices.…”

“…In most of these studies, the irradiations were performed with electrons of 2 MeV ͑or higher͒ energy, in which case damage is created in both Ga and N sublattices. Recent experiments 2,3 show that N sublattice defects could be selectively introduced by using 0.42 MeV electrons.…”

“…The defects introduced in electron irradiation of GaN have been studied earlier with electrical and optical methods, [1][2][3] optical detection of electron paramagnetic resonance ͑ODEPR͒, [4][5][6][7] and positron annihilation spectroscopy 8 as well. However, only in the most recent studies 2,3,7 could the measurements be performed in samples with both low impurity content and low dislocation densities, [9][10][11] allowing more accurate observations of the isolated intrinsic point defects.…”