Random telegraph noise and excess leakage current due to extended defects in GaN pn and p–i–n diodes on Si substrate

Mechanisms of excess leakage current (ELC) and random telegraph noise (RTN) fluctuations are investigated in p-GaN/n-Al0.03Ga0.97N (pn) and p-GaN/i-Al0.2Ga0.8N/n-Al0.03Ga0.97N (p–i–n) diode devices on Si substrates. RTN at both bias polarizations is observed in devices exhibiting reverse ELC associated with localized light emission spots due to extended defect (ED). Analysis of RTN amplitude and mean pulse widths as a function of bias indicates that RTN is due to fluctuations in ELC. The RTN shows large relative amplitude up to 30% at room temperature and 50% at 78 K. In addition, a weak temperature dependence of ELC is observed at reverse bias, which indicates that the ELC flows through a narrow constriction with a high electric field at ED. Impurity segregation and strain-induced bandgap reduction at a dislocation are considered to be the origin of the constriction. The observed forward bias dependence of RTN mean pulse widths is explained in terms of capture and/or emission events on an RTN-controlling defect which is located in the constriction. An RTN model for p–i–n diodes is proposed, which relates the experimental data to the spatial positions of recombination centers and the RTN-controlling defect.