Demonstration of avalanche capability in polarization-doped vertical GaN pn diodes: study of walkout due to residual carbon concentration

For the first time, we demonstrate and investigate the avalanche capability in vertical GaN-on-GaN pn diodes with polarization doping. Specifically: (i) we prove that the analyzed devices have avalanche capability, and we describe the dependence of breakdown voltage and leakage on temperature and monochromatic illumination; (ii) we demonstrate the presence of avalanche walkout, i.e. a recoverable increase in breakdown voltage induced by stress in avalanche conditions; (iii) we describe the time-dependence of avalanche walkout as a function of temperature, and demonstrate that walkout is caused by charge trapping due to residual carbon; (iv) we calculate the related activation energy and propose a model able to explain the experimental data. The reported results are of the utmost importance for the improvement in performance of high-voltage avalanche-capable GaN diodes.