Interface Fermi level pinning in a Cu/p-CuGaS2 Schottky diode Original Research Article

A Schottky contact to p-type CuGaS2 that showed the highest rectification ratio of approximately 500 ever reported was realized using a Cu electrode on a HF/HNO3-treated surface, as well as an excellent Au ohmic contact on a HF-etched surface. The effective Schottky barrier height of 0.9 eV was obtained from the current–voltage and capacitance–voltage characteristics. The value was smaller by 1.1 eV than that calculated from the values of the work function of Cu and electron affinity of CuGaS2. The results indicated a surface pinning of the Fermi level to certain acceptor-type gap states below the midgap.