Al₂O₃-passivated AlGaN/GaN HEMTs by using nonvacuum ultrasonic spray pyrolysis deposition technique

This letter reports, for the first time, the Al₂O ₃-passivated AlGaN/GaN high electron mobility transistors (HEMTs) by using the nonvacuum ultrasonic spray pyrolysis deposition (USPD) technique. The Al₂O₃ was devised as the surface passivation layer to effectively suppress leakage current and to reduce RF drain current collapse. The surface oxide has been characterized by using electron spectroscopy for chemical analysis, energy-dispersive X-ray spectroscopy, and transmission electron microscopy (TEM). With respect to an unpassivated device, the Al ₂O₃-passivated HEMT has demonstrated superior improvements of 24.2% in maximum drain-source current (I_DS, _max), 33.6% in maximum extrinsic transconductance (g_mmax), 46.8% in two-terminal breakdown voltage (BV_GD), and 45.3% in three-terminal off-state breakdown voltage (BV_off). The corresponding improvements achieved are 9.1%, 16.1%, 61.3%, and 55.7% for I _DS,_max) , g_m ,_max) , BV _GD) , and BV_off) , respectively, as compared with passivation in Si₃N₄ HEMTs. Besides, reduced interface density (D_it) and about two-order decreases in the leakage current are also achieved in the Al₂O₃-MOS diode using USPD with respect to a Si₃N₄-MIS diode.