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.