Fabrication of Si/SiGe quantum point contacts by electron-beam lithography and shallow wet-chemical etching

Abstract

We present a low-damage processing technique for fabricating quantum point contacts (QPCs) in the two-dimensional electron gas (2DEG) of a strained Si/Si0.7Ge0.3 heterostructure. The result is a QPC conductance characteristic which at T = 4.2 K exhibits a series of smeared step-like features. The QPCs were fabricated with a novel technique which combines electron-beam lithography with low-damage selective wet-chemical pattern transfer. The constriction of the QPC is formed by an etched groove with a break w positioned at the mesa center of a field-effect device perpendicular to the transistor channel. After subtracting a series resistance of 800 Ω five quantum steps can be observed in the differential conductance each of them contributing 4e2/h. We attribute the steps to the quantum-ballistic 1D-transport through the constriction. © 2002 Elsevier Science B.V. All rights reserved.