Improvements of AIN/GaN MISFET DC and RF characteristics with in situ deposited Si3N4

The DC and RF characteristics of AlN/GaN metal insulator semiconductor field effect transistors (MISFETs) on sapphire substrate with in situ deposited Si₃N₄ is presented. A 2 nm-thick Si₃N₄ was in situ deposited directly on the AlN barrier layer by the same metal organic chemical vapour deposition system as the one used for growth of the epitaxial layers. Large improvements of AlN/GaN MISFET DC and RF characteristics were observed with in situ deposited Si₃N₄. Fabricated AlN/GaN MISFETs with 1 m gate length and 200 m width showed a maximum drain current density of 403 mA/mm and a peak extrinsic transconductance of 206 mS/mm. Current gain cutoff frequency (f_T) and maximum oscillation frequency (f_MAX) were found to be 10.2 and 32.3 GHz, respectively.