## 3 Results and Discussion
In turn, the Chantre-Bois model applied here for comparison employs a different approach, where the local effective mass of the electron trapped at the defect level is an adjustable parameter denoted as \(\alpha^{-1}\). This parameter describes the localization of the electron wavefunction at the trap level and, therefore, its interaction with the lattice as well. In this study, \(\alpha^{-1}\) was individually determined for each trap state and estimated to be 1.67 \(\times\) 10\({}^{-3}\) A, 5.65 \(\times\) 10\({}^{-3}\) A, and 1.5 A for traps with Ec-2.05 eV, Ec-2.75 eV, and Ec-3.33 eV, respectively. Since \(\alpha^{-1}\sim~{}1/\sqrt{m}\), smaller values correspond to a higher effective electron mass and, thus, enhanced localization of the trapped electron wavefunction, as expected for deep trap states [6]. The only \(\alpha^{-1}\) value reported so far in the literature is for the E2 trap in n-GaN (Ec-0.56 eV), which is relatively shallow in comparison with midgap states, and was estimated to be 3.3 A [21]. This result is comparable to \(\alpha^{-1}=\) 1.5 A for a trap with Ec-3.33 eV found in this study. In contrast, the midgap states exhibited significantly lower values of \(\alpha^{-1}\), suggesting a strong coupling to the lattice, as previously reported in other experiments [1; 2; 3; 4]. Furthermore, an important distinction between the models is their applicability to the data measured at different temperatures. As indicated in Equation (5), the exponential component of the Chantre-Bois model approaches zero at low temperatures, resulting in \(\sigma=\) 0. Consequently, this model should be applied to the experimental data carried out at high temperatures. However, as was suggested by [PERSON] [28], due to a relatively high effective phonon energy, \(\varepsilon\sim\) 80 meV, the Chantre-Bois model in SiC could be efficient at temperatures above 1000 K, which is beyond the practical temperature range in most experiments. Since the effective phonon energy in GaN is comparable to SiC (\(\varepsilon_{\text{GaN}}\)\(\sim\) 50-60 meV), it is expected that similar restrictions regarding the temperature limit of the model application should be considered for GaN as well. In turn, the Passler model, presented in a more generalized form, as given in (4), has no limitations in terms of temperature and can be effectively applied across low- and high-temperature ranges. Consequently, the experimental data fitting with the Passler model is expected to provide more precise trap parameters than that determined from the Chantre-Bois model. Finally, the d\({}_{\text{FC}}\) and E\({}_{\text{T}}\) obtained in this study from the Passler model for a trap with Ec-2.75 eV (E\({}_{\text{T}}\) = 2.61 eV and d\({}_{\text{FC}}\) = 0.3 eV, given in Table 1) are consistent with previously published reports where trap levels of E\({}_{\text{T}}\) = 2.6 eV and d\({}_{\text{FC}}\) = 0.4 eV were found using the Passler model [28; 29], and this trap level was assigned to carbon-related (C\({}_{\text{i}}\) or C\({}_{\text{N}}\)) defects [29]. Since both E\({}_{\text{T}}\) and d\({}_{\text{FC}}\) reported in refs. [29; 30] are in good agreement with the results found in this study, we suggest that both trap states have the same origin. Unfortunately, the trap level with Ec-2.05 eV has never been reported before so a detailed analysis of this trap level could not be carried out. Therefore, the origin of this particular trap state level is still unknown.