Ruthenium based Schottky contacts on n-type GaN

The paper presents the investigation of ruthenium based Schottky contact to n-GaN:Si layers with different Si concentration grown by metalorganic vapour phase epitaxy (MOVPE) technique. Metallizations of ruthenium/gold were evaporated by an electron gun (Ru) and resistance heater (Au). The contacts were sequentially annealed at rapid thermal annealing (RTA) system under nitrogen ambient at various temperatures from 200degC to 650degC. The time of annealing process was 2 minutes. The barrier height of ruthenium based Schottky contacts to n-GaN MOVPE epitaxial layers were studied in a function of annealing temperature by current-voltage (I-V) method on dedicated test structures. The barrier heights of as-deposited Au/Ru/n-GaN Schottky contacts were evaluated and found to be 0.61 eV (n_d=9.9times10¹⁶ cm³) and 0.19 eV (n_d=8times10¹⁷ cm^-3). It was established that the temperature of 500degC was the most suitable for obtaining the highest values of Schottky barrier height (SBH) like 1.1 eV (n_d=9.9times10¹⁶ cm^-3) and 0.51 eV (n_d=8times10¹⁷ cm^-3) of Schottky contact based on ruthenium.