Surface States and Barrier Height at Metal-GaAs Interface

Abstract

Metal GaAs Schottky barriers have been prepared by vacuum deposition of films of various metals onto chemically etched n-type GaAs substrates. The diodes exhibit nearly ideal C-V and I-V characteristics with n values of 1.1 or less. The barrier height values derived from the I-V characteristics of the various contacts are found in agreement with those obtained from the C-V measurements only when the measured value of ideality factor n is also included in the expression for the saturation current Is. An estimate of the surface state density and the position of the neutral level at the metal-GaAs interface has been made from the observed dependence of barrier height on the metal work function φM employing the most recent values of φM. Surface states play a dominant role in the formation of the barrier and their density is 3.4×1014 eV-1cm-2 on the etched surfaces of GaAs.