Single-electron transistors in GaN/AlGaN heterostructures

We report transport properties of two single-electron transistors (SETs) on a GaN/AlGaN heterostructure. The first SET formed accidentally in a quantum point contact near pinchoff. Its small size produces large energy scales (a charging energy of 7.5 meV and well-resolved excited states). The second, intentionally fabricated SET is much larger. More than 100 uniformly spaced Coulomb oscillations yield a charging energy of 0.85 meV. Excited states are not resolvable in Coulomb diamonds, and Coulomb blockade peak height remains constant with increasing temperature, indicating that transport is through multiple quantum levels even at the 450 mK base electron temperature of our measurements. Coulomb oscillations of both SETs are highly stable, comparable to the best GaAs SETs. (c) 2006 American Institute of Physics.