The Role of Carbon Doping on Breakdown, Current Collapse, and Dynamic On-Resistance Recovery in AlGaN/GaN High Electron Mobility Transistors on Semi-Insulating SiC Substrates

Herein, the critical role of carbon doping in the electrical behavior of AlGaN/GaN high electron mobility transistors (HEMTs) on semi-insulating SiC substrates is assessed by investigating the off-state three-terminal breakdown, current collapse, and dynamic on-resistance recovery at high drain-source voltages. Extensive device simulations of typical GaN HEMT structures are conducted and compared with experimental data from published, state-of-the-art technologies to 1) explain the slope of the breakdown voltage as a function of the gate-to-drain spacing lower than GaN critical electric field as a result of the nonuniform electrical field distribution in the gate-drain access region; 2) attribute the drain current collapse to trapping in deep acceptor states in the buffer associated with carbon doping; and 3) interpret the partial dynamic on-resistance recovery after off-state stress at high drain-source voltages as a consequence of hole generation and trapping.