Barrier height at the interface between metal and polar AlxGa1− xN (0 ≤ x ≤ 1) epitaxial films was investigated using X-ray photoelectron spectroscopy and interface induced gap states (IFIGS) model. The opposite nature of polarization charge yields a significantly lower barrier height in N-polar AlxGa1−xN surface compared to the III-polar counterpart. Accordingly, IFIGS model indicate that III-polar AlxGa1−xN films are advantageous for Schottky contact formation for x < 0.3, whereas N-polar films offer a significantly lower knee voltage and ON-state resistance than the III-polar counterpart for x ≥ 0.3. Furthermore, N-polar AlxGa1−xN films are expected to offer a lower ohmic contact resistance than the III-polar counterpart for all values of x. The analysis performed in this work highlight the importance of N-polar Al-rich AlxGa1−xN epitaxial films for extending the figures of merit in future ultra-wide band gap semiconductor Schottky diodes.
