Physical Insights Into Electron Trapping Mechanism in the Carbon-Doped GaN Buffer in AlGaN/GaN HEMTs and Its Impact on Dynamic On-Resistance

In this work, a well-calibrated computational framework is used to probe the physical mechanisms leading to electron trapping in the carbon-doped GaN buffer in AlGaN/GaN HEMTs. Device variants having higher lateral electric field were found to exhibit a drastic increase in dynamic ON resistance beyond a critical drain stress voltage. Computations were done while considering trapping on the device surface, with and without accounting for hot electrons, as well as trapping in the GaN buffer. Detailed analysis established electron injection and trapping in the C-doped GaN buffer to be responsible for the observed dynamic ON resistance behavior. Physical insights are provided into the electron injection and trapping behavior by analyzing field evolution near the field plate edge, field-enhanced trapping, and its impact on the leakage current path within the GaN buffer. Finally, the proposed mechanism of field-enhanced electron trapping is validated by computations with device variants having field-independent trapping process and different buffer trap activation energies.