Silicon N-Channel Normally-Off Insulated-Gate Field-Effect Transistors

Abstract

Characteristics of n-channel normally-off insulated-gate field-effect transistors (IGFETs) are studied theoretically and experimentally. The obtained theoretical drain current is as follows:- I D =- I D O e q ( V G S - V T O )/ m k T ·(1- e - q V D S / k T ) where I D O is a constant, V G S and V T O are gate potential and the threshold voltage to make the onset of inversion, V D S is drain to source bias and m is reciprocal slope which is numerical constant determined by the parameters of the given FET. As predicted by the theory, experimental log I D vs V G S relation exhibits excellent linearity in the low level. The reciprocal slope and the thereshold voltage for the intrinsic drain current are influenced by the surface states as much as by the fixed charges located at the interface. P-type (100) oriented substrate wafer of u p more than 14 is needed to make n-channel normally-off IGFET in the present technique, where u p is a normalized Fermi potential of the substrate.