Metal-Semiconductor Contacts with Thin Interfacial Films

Abstract

The effect of the presence of a thin film of a highly doped semiconducting material or an insulator at the interface between a metal and a semiconductor on the electrical characteristics of the m-s contact is discussed. The increase in barrier height (δφß) calculated earlier for an interfacial layer of uniform doping is compared with the increases calculated for different impurity distributions in the doped layer.

A change in barrier height caused by the presence of a thin interfacial layer is however accompanied by an increase in the value of the ideality factor n, which is not desirable. The factors on which δφß depend are discussed and a compromise is suggested for achieving significant change of barrier height, keeping n at a low value.

If a thin insulating layer is present at the interface between a metal and a semiconductor, the barrier height is again affected, the amount and nature of change (increase or decrease) of the barrier height depending mainly on the character of the interfacial layer and surface conditions. Earlier work done on this subject is briefly reviewed. The effect of the presence of an interfacial layer on the ideality factor n is considered and inaccuracies involved in the determination of barrier height and Richardson's constant from I—V and C—V data are pointed out.