Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

Abstract

We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are de ned by the integration of side and top gates in a single device. In this con guration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of HfO2 or Al2O3/HfO2 composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current Ig < 10 −11 A at gate voltages |Vg| < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-o voltage at Vg = −3.5 V at a cost of Ig ≈ 10−6 A, which has been identi ed as a bulk leakage current.