p-GaN HEMT-on-SiC Structural Optimization for High Drain Current and High Threshold Voltage

Normally-OFF (enhancement type) p-type Gallium Nitride (GaN) gate HEMT-on-Silicon Carbide (SiC) exhibiting a high breakdown voltage and large value of saturation current density is demonstrated in this paper. Benefiting from Aluminium Nitride (AIN) nucleation, Indium Nitride (InN) nucleation and Silcon Nitride (Si3N4) passivation layers with better handling of electric field lines on gate side and low drain leakage current, the structure with gate-to-drain length of 6 Mm shows a breakdown voltage (Vbr) of 840 V at 100 MA/mm drain current. The device shows a threshold voltage (V th) value 1.98 V at a drain current (Ids) of 100 MA/mm, an ON-current/OFF-current ratio (Ion/Ioff) of 1.7×109, a small specific ON-condition resistance (Ron) of 2.5 ohm.cm2, a high value of drain current density (0.316 A/mm) at gate voltage (V gs) of 8 V. A sub-threshold slope of 77 m V /dec is obtained. A high trans-conductance of 69 mS/mm is achieved. When Vgs is 8 V, the device exhibit low gate current (Igs) value (22.3 MA/mm). These results show huge potential of p-GaN gate structure HEMT-on-SiC for power application.