Technology and electrical properties of ohmic contacts and Schottky diodes on homoepitaxial layers grown on (100) diamond surfaces

A general view of the key issues which have to be surmounted for building elementary devices such as Schottky diodes on homoepitaxial p-type diamond layers is presented. The growth process of double homoepitaxial layers, comprising a stack of both high and low boron doped films, is described and boron concentrations are analysed by means of cathodoluminescence. The methods used for masking, performing lithography on 3 × 3 mm2 samples and etching are delineated. Several ohmic contacts are compared. Surface treatments necessary for the Schottky diode technology are analysed and discussed. Two methods for achieving adherent Schottky contacts are compared and the electrical characteristics of diodes are studied as a function of the morphology, defect content and doping of the diamond layer, metal stack which is used, temperature history of the sample and passivation post-processes such as dry etching.