Passivation of the SiNx/GaAs (110) interface

Passivation of the SiNx/GaAs (110) interface was performed with different surface treatments including sulphur passivation and a Si or Si/Ge interface control layer on sulphur-passivated surfaces prior to silicon nitride deposition. The interface state density was measured with capacitance–voltage (CV) measurements of metal–insulator–semiconductor capacitors fabricated on the passivated surfaces using remote plasma-deposited silicon nitride as the gate insulator. The interface structures of the capacitors were analyzed by X-ray reflectivity and X-ray photoemission spectroscopy. It was found that the Si/Ge/S multilayer passivation approach led to the best CV results for an n-type substrate. The results also show that sulphur passivation could suppress As(Ga) segregation and that the interfacial atomic structure was not the only factor that determines the passivation. By comparing the quasi-static and high-frequency (1 MHz) CV data, we found that the minimum interface state density of the fabricated capacitors made on n-type substrates was about 1012 eV−1 cm−2.