Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

M. Czapkiewicz a, G. Cywiński b, K. Dybko a, M. Siekacz b, P. Wolny b, S. Gierałtowska a, E. Guziewicz a, C. Skierbiszewski b and J. Wróbel a aInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warszawa, Poland bInstitute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland

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We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, 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-off voltage at Vg = - 3.5 V at a cost of Ig ≈ 10-6 A, which has been identified as a bulk leakage current.

DOI: 10.12693/APhysPolA.122.1026 PACS numbers: 73.40.Qv, 73.61.Ng, 73.23.-b