WN_x Schottky diodes on plasma treated GaAs

The influence of the GaAs surface condition on the properties and thermal stability of WN_x Schottky diodes on GaAs has been studied by performing in situ H₂ and N₂ plasma treatments just before the WN_x sputter deposition. The WN_x/GaAs contacts have been investigated by x‐ray photoelectron spectroscopy, Rutherford backscattering, nuclear reaction analysis, secondary ion‐mass spectroscopy, x‐ray diffraction, and transmission electron microscope and correlated to electrical current‐voltage and capacitance‐voltage measurements. A strong correlation was found between the diode properties and the surface conditions, both for the as‐deposited samples and for samples annealed in the range 700–850 °C. Poor rectifying properties were obtained for the plasma‐cleaned diodes due to the cumulative effects of plasma cleaning and sputter deposition. After annealing, improved characteristics were generally found. The highest Schottky barrier height values φ^I‐V=0.76 V, which were found for the H₂ plasma treated diodes annealed at 800 °C, were almost independent of the WN_x composition and sputtering conditions. The H₂ treated samples also showed the smoothest WN_x/GaAs interface. HCl cleaned and N₂ treated surface also showed high‐barrier height and small interfacial reactions after high‐temperature annealing.