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

Interfacial properties of Si3N4/Si/InGaAs metal-insulator-semiconductor structures are studied in detail. Both the Si3N4 and Si layers are deposited in-situ in an ultrahigh vacuum chemical vapor deposition chamber on as-grown MBE In0.53Ga0.47As surfaces. In-situ deposition is found to be crucial to obtain low interface-trap density. By incorporating a pseudomorphic Si interlayer up to 4 monolayers, it is shown that frequency dispersion of CV curves reduces as the thickness of the Si layer increases. A minimum frequency dispersion is obtained, which is the 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 present results, therefore, indicate that the density of tunneling related traps is reduced as the thickness of the Si interlayer increases. In this paper, the conductance and quasi-static CV methods are also used to characterize the interface trap density. The minimum interface trap density 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 interface 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 transconductance of over 200 mS/mm for devices with 2.2 mum gate length.