Electrical characteristics of surface-stoichiometry-controlled p-GaN schottky contacts

Experimental results of Au/Ni Schottky contacts formed on three kinds of p-GaN layers, which were grown at different turn-off temperatures (300, 600, and 900 °C) of NH₃ gas supply (T_NH3) upon cooling at the end of growth to control the surface stoichiometry are reported. In the internal photoemission results, the Schottky barrier heights of all the samples were as large as around 2.2 eV, and a slight increase of 0.1 eV was observed when T _NH3 decreased from 900 to 300 °C. At the same time, carrier capture and emission from acceptor-like midgap-level defects decreased as T _NH3 decreased. The N-rich cooling condition tends to passivate the acceptor-type defects or create donor-type defects for compensation, and the pinning position at the interface might be moved slightly toward the conduction band edge.