High-Performance Enhancement-Mode Al2O3/AlGaN/GaN-on-Si MISFETs With 626 MW/ Figure of Merit

In this paper, the partial gate recess for performance improvement of enhancement-mode (E-mode) GaN power devices is experimentally demonstrated. The gate recess with a careful control of the recess depth was performed with an optimized recessed barrier thickness of ~1.5 nm that is thin enough to completely deplete the 2-D electron gas channel in the gate region. Meanwhile, the remaining barrier preserves the as-grown quantum well of the heterostructure physically intact and thus, effectively mitigates the lattice damage caused by gate recess. The fabricated E-mode Al₂O₃/AlGaN/GaN MISFETs deliver a threshold voltage (V_TH) of +1.5 V. The maximum drain current density (I_D,max) and transconductance (G_m,max) are 693 mA/mm and 166 mS/mm, respectively. The MISFETs with an L_GD of 10 μm feature an OFF-state breakdown voltage of 860 V at a leakage current of 1 μA/mm. The corresponding specific ON-resistance (R_ON,sp) is as low as 1.18 mΩ·cm² yielding a high-power figure of merit of 626 MW/cm². In comparison with the reference MOSFETs by fully gate recess, the respectably improved device performance of the MISFETs attributes to the enhanced electron mobility achieved by the partial gate recess.