Self-terminating contactless photo-electrochemical (CL-PEC) etching for fabricating highly uniform recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs)

Contactless photo-electrochemical (CL-PEC) etching was used to fabricate recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). Self-termination of observed during CL-PEC on an AlGaN barrier layer whose residual thickness had a uniform value 6 nm overall the same chip. After tetramethylammonium hydroxide post-treatment, root-mean-square roughness etched surface around 0.4 nm, which smoothness comparable that unetched surface. Recessed-Schottky HEMTs showed positive shift in Vth, suppression drain leakage currents, and improvement subthreshold-slope as compared with planar-gate HEMTs. By applying metal–insulator–semiconductor (MIS)-gate structure, gate currents were significantly reduced, leading increased input dynamic range. Furthermore, standard deviations (σ) Vth CL-PEC-etched recessed-Schottky recessed-MIS very small, 5.5 16.7 mV, respectively. These results process is promising for fabrication having excellent uniformity normally-off device operations.