High Performance Normally-Off Al2O3/AlGaN/GaN MOS-HEMTs Using Diffusion-Controlled Interface Oxidation Technique

摘要

In this paper, a novel and promising interface treatment method in GaN-based MOS-HEMTs, diffusioncontrolled interface oxidation (DCIO) technique was reported. After chemical cleaning and in situ nitridation plasma surface pretreatment, 1 nm Al₂O₃ diffusion-controlled interfacial layer (DCIL) was pre-deposited, followed by plasma-assisted oxidation whose rate was controlled by the diffusion of oxygen radical through Al₂O₃ DCIL. Compared with the conventional reaction-controlled surface oxidation (RCSO), DCIO is much slower, resulting in high quality of crystalline-like AlGaON interfacial layer. DCIO leads to a further decrease in interface charges by 7.6×10¹² cm^-1 and 3.8×10¹² cm^-1 compared with the case with and without oxidation, respectively. By using DCIO technique in combination with postdeposition metallization annealing, high-performance recessed-gate Al₂O₃/AlGaN/GaN normally-off MOS-HEMTs were achieved, with V_th=2.75 V, large output current of 865 mS/mm, g_max=271 mS/mm, and ION/IOFF over 10⁹.