A novel manufacturing process of AlGaN/GaN HEMT for X-band high-power application on Si (111) substrate

In this paper, successful operation at 10 GHz of 0.5 μm gamma gate AlGaN/GaN high electron mobility transistor (HEMT) is demonstrated on Si (111) substrate. Various material and processing approaches regarding double surface passivation and post-gate annealing processes are evaluated in terms of device performances. In order to achieve better immunity to current collapse effects, we conducted experiments that investigate the relationship between the HEMTs electrical characteristics and different passivation films (SiN_x or SiO₂) using plasma-enhanced chemical vapor deposition (PECVD). A post-gate nitrogen rapid thermal annealing (RTA) method done after the gate metallization process has shown better DC current-voltage output, transfer characteristics, and gate-drain breakdown voltage results compared to the as-fabricated HEMTs. A HEMT with a 0.5 μm gate length, exhibiting a maximum drain current density of 750 mA/mm, a peak transconductance of 220 mS/mm, a unity-gain cut-off frequency (f_T) of 24.6 GHz, and a maximum frequency of oscillation (f_MAX) of 45.4 GHz, was fabricated; the power performances demonstrate a 5.8 W/mm output power density and a 51% power added efficiency (PAE).