Electrical Properties of Metal-GaAs Schottky Barrier Contacts

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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 7×1013 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 2×1015 to 5×1017 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.