Investigating the Saturation Phenomenon of the Drain-Induced Barrier Lowering Effect on AlGaN/GaN High Electron Mobility Transistors with Schottky-Gate Structures

This study investigates the saturation phenomenon of the drain-induced barrier lowering (DIBL) effect in Schottky-gate gallium nitride (GaN) high-electron-mobility transistors (HEMTs) featuring T-gate structures. The threshold voltage ( V TH ) and DIBL under various drain voltages ( V D ) are examined through electrical measurements and Silvaco simulations. Experimental results reveal that the DIBL effect saturates at high V D . Furthermore, comparison of I D – V G characteristics between devices with and without T-gate structures indicates that the DIBL saturation phenomenon exclusively occurs in T-gate structures. To investigate the underlying mechanism, Silvaco simulations are conducted to analyze the electric field distribution, energy band diagrams, and two-dimensional electron gas (2DEG) concentrations under high V D . The results demonstrate that the T-gate structure effectively suppresses the DIBL effect by dispersing the electric field, reducing the 2DEG concentration, and increasing the voltage drop across the drift region. Additionally, the influence of T-gate geometry on DIBL suppression is systematically studied by varying T-gate extension lengths and heights. This analysis provides valuable insights into optimizing T-gate design for enhanced performance of GaN HEMTs under high drain bias conditions.