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 200°C to 650°C. 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
=9.9×10
¹⁶
cm
³
) and 0.19 eV (n
d
=8×10
¹⁷
cm
^-3
). It was established that the temperature of 500°C was the most suitable for obtaining the highest values of Schottky barrier height (SBH) like 1.1 eV (n
d
=9.9×10
¹⁶
cm
^-3
) and 0.51 eV (n
d
=8×10
¹⁷
cm
^-3
) of Schottky contact based on ruthenium.