Electrical characteristics of Pt∕Au Schottky contacts to plasma-etched AlGaN

The effects of surface treatment using Ar and Cl2∕BCl3 inductively coupled plasmas on the rectifying characteristics of Pt∕Au contacts to AlxGa1−xN (x=0.1–0.5) were investigated. Plasma treatment increased the conductivity of Al0.1Ga0.9N surfaces, making the rectifying contacts into Ohmic contacts. For higher Al-content AlGaN, the Schottky diodes turned leaky after Cl2∕BCl3 plasma treatment, where damage creation and etching occur simultaneously, whereas the diodes become more rectifying upon Ar plasma exposure, in which plasma damage accumulates. A time-dependent study of Ar plasma treatment supports the hypothesis that the energy level of plasma damage in high-Al content AlGaN may be damage density dependent, and damage accumulation during Ar plasma exposure results in a high-resistivity region compensated by deep-level defect states.