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

We report on the influence of different pre-etch methods on specific contac t parameters of GaN contacts. For these investigations we used ex situ chem ically assisted ion beam etching and in situ sputter etching before metal d eposition. The electrical contact parameters were determined using the exte nded circular transmission line model (CTLM). For nitrogen as an etching ga s we obtained rectifying character (Schottky) of metal-n-GaN contacts compa red with mostly linear (Ohmic) behaviour for conventional etching gases suc h as Ar or ArCl2. We assume that a decrease of N vacancies caused by the N- 2 treatment is responsible for the Schottky behaviour of these contacts. Pr e-etch sputtering with Ari ions reduces on the one hand the specific contac t resistance rho(C) but on the other hand the CTLM modal reveals that simul taneously the sheet resistance R-sk in the near-surface region increases.