CHARACTERISTICS OF INSITU DEPOSITED SI3N4 SI/IN0.53GA0.47AS METAL-INSULATOR-SEMICONDUCTOR STRUCTURES/

Interfacial properties of Si3N4/Si/InGaAs metal-insulator-semiconducto r structures are studied in detail. Both the Si3N4 and Si layers are d eposited in-situ in an ultrahigh vacuum chemical vapor deposition cham ber on as-grown MBE In0.53Ga0.47As surfaces. In-situ deposition is fou nd to be crucial to obtain low interface-trap density. By incorporatin g a pseudomorphic Si interlayer up to 4 monolayers, it is shown that f requency dispersion of CV curves reduces as the thickness of the Si la yer increases. A minimum frequency dispersion is obtained, which is th e same as that of the Si3N/(bulk Si) interface, when the thickness of the Si is 3 to 4 monolayers. In a recent paper, we have shown that the frequency dispersion is due to tunneling related trapping. The presen t results, therefore, indicate that the density of tunneling related t raps is reduced as the thickness of the Si interlayer increases. In th is paper, the conductance and quasi-static CV methods are also used to characterize the interface trap density. The minimum interface trap d ensity of these samples is found to be of the order of low 10(11) eV-1 cm-2 depending on the deposition conditions. Dependence of the interf ace trap density on the deposition temperature will also be reported. Metal-insulator-semiconductor depletion-mode field effect transistors fabricated on in-situ deposited samples exhibit a maximum transconduct ance of over 200 mS/mm for devices with 2.2 mum gate length.