Optical characterization of AlxGa1−xN/GaN high electron mobility transistor structures

The high frequency conductance G of a quantum point contact was studied for View the MathML source. While the real part R(G) remains unchanged by frequency we observe a stepwise change of the imaginary part I(G) when adding additional conductance channels. The step height ΔI(G) is linear in frequency with a positive slope and thus has capacitive character with a ΔC per channel of a few fF.