Influence of pre-etching on specific contact parameters for metal-GaN contacts

摘要

We report on the influence of different pre-etch methods on specific contact parameters of GaN contacts. For these investigations we used ex situ chemically assisted ion beam etching and in situ sputter etching before metal deposition. The electrical contact parameters were determined using the extended circular transmission line model (CTLM). For nitrogen as an etching gas we obtained rectifying character (Schottky) of metal-n-GaN contacts compared with mostly linear (Ohmic) behaviour for conventional etching gases such as Ar or ArCl_2. We assume that a decrease of N vacancies caused by the N_2 treatment is responsible for the Schottky behaviour of these contacts. Pre-etch sputtering with Ar+ ions reduces on the one hand the specific contact resistance ρc but on the other hand the CTLM model reveals that simultaneously the sheet resistance R_sk in the near-surface region increases.