Trap studies on GaAs–Si3N4 interfaces

Abstract

The dynamic properties of GaAs–Si3N4 interfaces in IGFET structures were studied. It was observed that the charging of the interface states with electrons is very fast and approximately 90% of the interface charge is trapped within 1 ns of charging time. The studies indicated that two processes contribute to the discharge of the surface states. When the active layer is totally depleted, mainly leakage currents from the SI GaAs substrate discharge the surface states. When the active layer is not totally depleted, thermal electron emission from the interface dominates the discharge of surface states. A surface state trap level of 0.71 eV was measured. Furthermore, charging of surface states in an area adjacent to the gate was studied and it was observed that the charging occurs while the transistor is pinched off. Finally, current flow through the Si3N4 film was studied and it was concluded that these currents are too small to account for charging and discharging of interface states.