The Variation of Ohmic Contacts and Surface Characteristics on p-GaN Induced by Reactive Ion Etching

Abstract

Electron cyclotron resonance (ECR) reactive ion etch (RIE) was used to etch p-type GaN under a chlorine-based plasma. Rapid thermal annealing (RTA) and nitrogen plasma were used as post-RIE treatments to investigate the variation of Ni/Au contacts on p-GaN. RIE deteriorated the contact very much due to the induced nitrogen vacancies and damage on the p-GaN surface. The poor contact was improved by RTA treatment at 700°C for 3 min although the current-voltage curve was still nonlinear. The results from X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and grazing incidence X-ray diffraction measurements indicated that RTA at 700°C could reconstruct the ordered structure from the damaged p-GaN surface. Annealing at 500 or 900°C did not improve the contact due to the high oxygen content of the surface. plasma treatment could scarcely improve the contact. XPS and photoluminescence analyses revealed that the nitrogen plasma treatment increased the number of nitrogen vacancies as well as the nitrogen content of a p-GaN surface. These nitrogen atoms did not form tight bonds with GaN, and easily escaped from the surface by annealing. © 2002 The Electrochemical Society. All rights reserved.