Doping-dependent carbon atom transient ionization behavior and its impact on RON stability in GaN-on-Si HEMTs

Carbon doping is widely employed to form semi-insulating buffers and is regarded as detrimental to the on-resistance stability of GaN-based high-electron-mobility transistors due to off-state-stress-induced negative carbon charging. However, in this work, an abnormal phenomenon was observed in which carbon-doping-dependent dynamic on-resistance degradation was suppressed in heavily carbon-doped high-electron-mobility transistor samples. Substrate-biased current deep-level transient spectroscopy analysis indicates that band-to-band tunneling occurs more easily and intensively in devices with higher carbon concentrations, generating more electron–hole pairs. After removal of the negative substrate bias, the holes flow back to the carbon-doped region and compensate for the depletion effect of negatively ionized carbon atoms on the two-dimensional electron gas, thereby suppressing on-resistance degradation. These observations provide insight into the reliability mechanisms related to the dynamic stability of GaN-based high-electron-mobility transistor power devices.