Validity/invalidity of Schottky-Mott rules for Schottky contacts to III-V nitride semiconductor heterostructures

Carrier transport through the metal/semiconductor and metal/semiconductor/semiconductor (M/S/S) Schottky contact interfaces has been studied. Metal/n-GaN, metal/n-AlxGa1-xN, and metal/n-AlxGa1-xN/n-GaN diodes have been chosen for the study. It has been observed that, owing to the presence of the piezoelectric polarization field and a quantum well at the AlxGa1-xN/GaN interface, the AlxGa1-xN/GaN contacts exhibit properties distinctly different from those of the AlxGa1-xN contacts. The superiority of the AlxGa1-xN/GaN contacts to that of the AlxGa1-xN contacts largely disappears at high temperatures. While the GaN and AlxGa1-xN contacts appear to obey the Schottky-Mott rule, the AlxGa1-xN/GaN contacts tend to disobey it.