GaAs metal insulator field effect transistors with excellent intrinsic transconductance and stable drain currents using (NH/sub 4/)/sub 2/Sx chemical treatment

Abstract

Metal insulator semiconductor field effect transistors (MISFETs) and MIS capacitors are fabricated using Al metal-gate and PECVD silicon nitride (Si/sub 3/N/sub 4/) gate-insulator on commercial GaAs epitaxial wafers after treating the channel regions with (NH/sub 4/)/sub 2/S/sub x/. It is shown that the post metallization annealing (PMA) of these devices improves the transconductance and reduces the interface state density (D/sub it/) considerably. This is attributed to the additional passivation effect of hydrogen diffusing to the interface from the Si/sub 3/N/sub 4/ during the PMA. An intrinsic transconductance of 30.7 mS/mm which is 75% of the theoretical maximum limit of 40.5 mS/mm has been achieved using silicon nitride gate insulator thickness of 1100 /spl Aring/. Stability of the drain currents in these devices is demonstrated to be excellent.