Improvement of the Breakdown Voltage of GaN HEMTs Using a Back Electrode and a High-k Passivation Layer

A GaN-based high-electron-mobility transistor (HEMT) that couples a grounded electrode beneath the buffer with a TiO2 high-k passivation layer (BHK-HEMT) is investigated for enhanced off-state breakdown capability via simulation. The introduction of the back electrode can regulate the internal potential distribution from the bottom of the device and effectively alleviate electric field crowding near the gate. In addition, the high‑k dielectric layer further smoothes the field profile in the gate‑drain spacing. Simulation results show that the breakdown voltage (BV) for BHK-HEMT rises from 319 to 1336 V, with an improvement of 319%. In comparison with C-HEMT, the threshold voltage and transconductance of BHK-HEMT remain largely stable, accompanied by a minor decrease in the saturation drain current. As a result, the proposed structure attains a favorable equilibrium between BV and other electrical performance indicators.