Atomic layer etching-enabled interface engineering for enhanced carrier transport in GaN trench MOSFETs

In GaN trench metal–oxide–semiconductor field-effect transistors (MOSFETs), trench formation through dry etching inevitably introduces a high density of surface defects, which intensifies Coulomb scattering and degrades channel mobility (μ_ch). Herein, following conventional dry etching, atomic layer etching (ALE) was employed as a post-etch recovery process to mitigate trench damage induced by energetic plasma bombardment. Wafer-scale atomic force microscopy measurements demonstrated excellent uniformity in surface morphology after ALE treatment. Transmission electron microscopy revealed that ALE removed etch-induced damage more effectively than TMAH treatment. X-ray photoelectron spectroscopy, cathodoluminescence, secondary ion mass spectrometry, and capacitance–voltage measurements revealed that ALE effectively removed nitrogen vacancies (V_N) generated by plasma bombardment, thereby reducing trench interface trap density. Owing to the elimination of V_N and suppression of Coulomb scattering, the ALE-treated samples exhibited significantly enhanced electrical performance compared with untreated ones, with the threshold voltage increasing from (4.2 ± 0.2) V to (6.5 ± 0.3) V, the μ_ch increasing from (7.68 ± 0.58) cm²·V⁻¹·s⁻¹ to (24.58 ± 2.03) cm²·V⁻¹·s⁻¹, the saturation current density improving from 605 A/cm² to 1253 A/cm², and the specific on-resistance decreasing from 6.4 mΩ·cm² to 2.9 mΩ·cm². These results highlight the great potential of ALE in the application of GaN trench MOSFETs.