Optically and thermally detected deep levels in n-type Schottky and p+-n GaN diodes

N-Schottky and $p^{+}\mathrm{–n}$ GaN junctions are currently used for different technologies. A comparison of the deep levels found throughout the entire band gap of $\mathrm{n-}\mathrm{GaN}$ grown by metal-organic chemical vapor deposition under both configurations is presented. Both deep level optical spectroscopy and deep level transient spectroscopy measurements are used allowing the observation of both majority and minority carrier traps. Deep levels at $E_c{\mathrm{-E}}_t\text{=0.58–0.62,}$ 1.35, 2.57–2.64, and 3.22 eV are observed for both diode configurations, with concentrations in the ${\text{∼10}}^{14}{\text{–10}}^{16} {\mathrm{cm}}^{\mathrm{-3}}$ range. The 0.58–0.62 eV level appears correlated with residual Mg impurities in the $n$ side of the $p^{+}\mathrm{–n}$ diode measured by secondary-ion-mass spectroscopy, while the 1.35 eV level concentration increases by a factor of ∼4 for the Schottky junction possibly correlating with the carbon profile. The 2.57–2.64 eV level is a minority carrier hole trap in $\mathrm{n-}\mathrm{GaN},$ likely related to the yellow photoluminescence band, and is detected both optically from the conduction band (2.64 eV) and thermally from the valence band (0.87 eV).