Surface Morphology and Electronic Properties of ErSi₂

Abstract

The surface of ErSi₂, formed by the reaction of thin erbium layers with a single-crystal silicon substrate, is typically dominated by deeply penetrating regularly shaped pits. These pits are shown to have detrimental effects on the electronic performance of Schottky barrier diodes. Surface pits may be reduced in density or eliminated entirely (i) by the use of silicon substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition, (ii) by means of ion irradiation techniques or (iii) by reacting erbium with an amorphous silicon (a-Si) layer. In this investigation, planar ErSi₂ layers (pit free) are made using the third approach with a sample structure of a-Si/Er/c-Si where c-Si denotes crystalline silicon. The fast reaction between a-Si and erbium leads to a planar sample structure of ErSi₂/c-Si with little or no reaction between erbium and the c–Si substrate. The electronic performance of pit-free ErSi₂ diodes made in this manner is shown to be much superior to that of diodes made by reacting erbium with silicon substrates.