Electrical Properties of Metal-GaAs Schottky Barrier Contacts

Abstract

Experimental studies are reported concerning surface states and current transport properties of the Schottky barrier diodes prepared by evaporation of various metals under high vacuum on chemically etched n -type GaAs (111) surfaces. Surface state density, determined from a relation of the barrier height and vacuum work function of metals, amounts to 7×10 13 cm -2 eV -1 and the effective thickness of interfacial layer is estimated to be 3∼8 Å from an analysis of various diode characteristics. Density distribution of the surface states in the lower half of the band gap is derived. Dependences of current-voltage characteristics on donor concentration in the range 2×10 15 to 5×10 17 cm -3 and on temperature, 4.2 to 400°K, are accounted for in terms of thermionic-field emission and field emission theories. Effects of deep-lying donors on reverse characteristics and others are discussed. Changes in barrier properties by heat treatment at temperatures up to 400°C are presented.