Fig. 1. (a) Schematic diagram of Mg ion implantation in GaN. (b) SIMS results of Mg distribution in the GaN layer before and after annealing. (c) 2θ-ω XRD scan on (0002) and (1012) planes of as-grown GaN and Mg-implanted GaN with the post-annealing process; the inset shows the AFM morphology of GaN with Mg implantation and the post-annealing process.

Fig. 2. (a) Current-voltage (I-V) characteristics of the fabricated quasi-vertical GaN p-i-n diode with a Mg implanted p-type layer; the inset illustrates the cross-sectional schematic of the diode. (b) I-V results in linear plots. (c) Electroluminescence (EL) spectrum of the Mg ion-implanted GaN p-i-n diode; the inset displays the EL emission pattern.

Fig. 3. (a) Photo- and dark current measurements for the Mg ion-implanted quasi-vertical GaN p-i-n photodiode. (b) Spectral response characteristics at zero bias of the UV photodetector based on the Mg ion-implanted p-i-n diode (blue) and a commercially available GaN p-n photodiode (red).

Fig. 4. (a) Temperature-dependent leakage measurement. (b) Hopping conducting-based linear fitting between ln(J) versus E. (c) Linear fitting between α and 1/T5/4. (d) Poole–Frenkel emission-based linear fitting between ln(J) and E1/2.

Fig. 5. (a) Reverse-bias-dependent responsivity measurement at an optical power density of 2.5  mW/cm2 at 365 nm. (b) Dependence of photocurrent on the optical power density. (c) Schematic diagram of the electric-field-assisted photocarrier hopping.

Fig. 6. Time response characteristics of the Mg ion-implantation-based GaN p-i-n diode. (a) Response waveform in six repeated circles. Photocurrent (b) rise and (c) decay edge within one response pulse. (d) Decay waveform in exponential scale.