Effect of Oxidation using Ultraviolet Light and Ozone and Subsequent Nitridation using Electron Cyclotron Resonance Plasma on Gate Portion of GaAs Field-Effect Transistors

Abstract

A recess-gate-type n-channel depletion mode metal–semiconductor field-effect transistor (MESFET), a metal–oxide–semiconductor field-effect transistor (MOSFET) prepared by UV and ozone oxidation, and metal–insulator–semiconductor field-effect transistors (MISFETs) prepared by oxidation followed by nitrogen plasma treatment for different time durations with an electron cyclotron resonance system (oxinitridation) were fabricated using an ex-situ process and equally current controlled recessed wafers. The MISFETs, especially the longest-nitrided one, showed the highest pinch-off gate voltage (-1.5 V) and the highest peak transconductance (170 mS/mm) at a 0.9 V gate voltage. The MOSFET showed the largest drain current, whereas the longest-nitrided MISFET showed the smallest drain current, owing to the difference in applicable forward gate voltage. These were clearly confirmed with statistical data. The transconductance obtained reproduces that of our previous experiment, and its increase is due to the improvement of crystallographic order in the vicinity of the insulator/semiconductor interface. The different applicable gate voltage implies that the subsequent nitridation weakens the barrier effect of the oxidized layer. An AlGaAs layer, as the mother material for oxinitridation, improves it.