Recessed-gate AlGaN/GaN MIS-FETs with dual 2DEG channels

In this study, a normally-on AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) and a normally-off AlGaN/GaN metal-insulator-semiconductor field-effect transistor (MIS-FET) with recessed MIS gate are fabricated by dual-channel epitaxy structure. The recessed region is cleaned by dipping it into diluted buffered oxide etch (BOE), HCl, and tetramethylammonium hydroxide (TMAH) solutions. After cleaning, a 20 nm Al₂O₃ is deposited by atomic layer deposition (ALD). Then, the post-deposition annealing is executed. Non-recessed MIS-HEMT demonstrates a threshold voltage of −9.81 V, a high drain current of 660.76 mA mm⁻¹, and a small on-resistance of 6.47 Ω mm. Recessed gate MIS-FET shows a positive threshold voltage of 1.46 V with a drain current of 144.81 mA mm⁻¹. In addition, the devices present a high gate breakdown voltage of 26.5 V by non-recessed MIS-HEMT and 18.5 V by recessed MIS-FET. Both devices show a low I-V hysteresis under double sweep I _D-V _GS measurement.