Thermal stability of Pt- and Ni-based Schottky contacts on GaN and Al0.3Ga0.69N

In this work we analyse the performance of Pt- and Ni-based Schottky metallizations on AlxGa1-xN (x = 0, 0.31). An intermediate thin Ti layer is shown to enhance the thermal stability of Pt/Au, and leads to an increase of the Schottky barrier height. Pt/Ti/Au contacts on GaN provide a barrier height of 1.18 +/- 10.07 eV, increasing up to 2.0 +/- 0.1 eV on Al0.31Ga0.69N. Further improvement of Schottky contacts is achieved by surface passivation with plasma-enhanced chemical vapour deposited SiO2 or SixNy, which reduces the leakage current by two orders of magnitude and structural modifications in the metal due to thermal ageing.