Defect Donor and Acceptor in GaN

On the main irradiation-induced defect in GaN

“…16,18 For the conditions here, the correction was about 20%, and was included in the N T0 data shown in Fig. 3 The conclusion that both ED1 and ED2 have a thermal energy of about 0.06 eV is significant, because it resolves the major discrepancy with the Hall-effect experiment, 7 which also found an energy of 0.06 eV. Earlier DLTS analyses 8,10,12,17 had found much higher energies, 0.14-0.20 eV; however, in these cases, a single peak was assumed, Arrhenius plots were used to determine the energies, and the E contribution to the energies was not considered.…”

“…5 Recently, a strong effort by several groups has been devoted to the study of irradiation-induced defects in GaN and related compounds. [6][7][8][9][10] Most of the results are still not fully understood, but some useful conclusions have already emerged. As an example, for 30 years the N vacancy V N has been considered to be the dominant donor in GaN, 11 but it has just recently been shown that this assumption is not true, 7 at least for the best, present-day material.…”

“…7 ͑Here, E C and E T denote the energies of the conduction-band minimum and trap, respectively.͒ However, the dominant deep-level transient spectroscopy ͑DLTS͒ defect, for several different types of irradiation, is an electron trap, with an Arrhenius-determined energy of about 0.14-0.20 eV below the conduction band. 8,10,12 In this letter, we show that the usual Arrhenius analysis is not sufficient and that the true thermal energy ͑i.e., E C ϪE T ͒ is indeed about 60 meV.…”

“…where k is the Boltzmann constant, Cϭ16 m n *k 2 /h 3 ϭ6.57 ϫ10 20 cm Ϫ2 s Ϫ1 K Ϫ2 for n-type GaN, n (ϱ) is the capture cross section at Tϭϱ, E T0 is the thermal energy at Tϭ0 ͑the energy also determined from Hall-effect measurements 7 ͒, E is the barrier energy for the capture cross section, g 0 (g 1 ) is the unoccupied ͑occupied͒ state degeneracy, and ␣ is a parameter indicating the temperature dependence of the thermal energy (E T ϭE T0 Ϫ␣T). We assume that ␣Ϸ0, for a level close to the conduction band, and we also assume that g 0 /g 1 ϭ1/2, appropriate for V N .…”

Deep centers in n-GaN grown by reactive molecular beam epitaxy

“…10 Although there is a significant difference in the activation energy for the electron-irradiation-induced Hall donor center ͑0.07 eV͒ and the DLTS center ͑0.18 eV͒, we still believe that the DLTS center, trap E, might be related to the N vacancy, since an activation energy for the capture cross section could be involved in the apparent DLTS activation energy of 0.18 eV. Moreover, both centers have similar production rates and annealing behavior.…”