A New Method to Estimate Surface Donor Density (N _TD ) in AlGaN/GaN HEMT by Validated DCT Simulations

This work proposes a new method to estimate surface donor density ( N TD ) in AlGaN/GaN high‐electron‐mobility transistors (HEMTs) using validated drain current transient (DCT) simulations. The DCT signal is actually induced by an acceptor‐type buffer trap at E C −0.65 eV. Although the DCT signal amplitude (Δ I DS ) reflects ionized acceptor density ( N TA − ) in the buffer, N TA concentration is not self‐sufficient to predict the actual Δ I DS variations. The simulation analysis reveals that 2D electron gas (2DEG) density augments with increasing N TD , resulting in more electron trapping under the gate edge region (towards the drain end) of the buffer. The increased buffer trapping raises the Δ I DS signal during the emission transient. After multiple simulation runs, N TD for the donor trap at E C −0.2 eV is estimated to be 1.3 × 10 13 cm −2 , based on the validated DCT properties at different temperatures. The matched output admittance ( Y 22 ) and forward transfer admittance ( Y 21 ) parameters also yield similar N TD =1.4 × 10 13 cm −2 , thus verifying the DCT findings. N TD is often assumed in simulations, so the extracted N TD (1.3–1.4 × 10 13 cm −2 ) benefits the GaN HEMT community for accurately modeling the surface donor properties.