Suppression of interface states between nitride-based gate dielectrics and ultrathin-barrier AlGaN/GaN heterostructure with in situ remote plasma pretreatments.

A silicon nitride (SiN_x) film deposited at 500 °C by plasma-enhanced atomic layer deposition (PEALD) is employed as the gate dielectric for GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs). An interface enhancement technology featuring in situ low-damage NH₃/N₂ remote plasma pretreatments (RPPs) is developed prior to the SiN_x gate dielectric deposition, which contributes to an improved surface morphology while remarkably suppressed interface oxides. It is revealed by constant-capacitance deep-level transient spectroscopy that both shallow and deep states at the PEALD-SiN_x/III-nitride interface are reduced by about one order of magnitude by the RPP. The in situ RPP and PEALD-SiN_x gate dielectric process are implemented into fabrication of enhancement-mode MIS-HEMTs on an ultrathin-barrier AlGaN/GaN heterostructure technology platform. The fabricated MIS-HEMTs deliver an improved threshold stability and maximum output current as compared with devices without the RPP. [ABSTRACT FROM AUTHOR]