Fabrication of aluminum single-electron transistors with low resistance-capacitance product

The optimum speed and sensitivity of a single-electron transistor (SET) depend crucially on the resistance-capacitance (RC) product of the tunnel junctions. We present a fabrication method of aluminum single-electron transistors with a high percentage of working devices (80%) and record low RC products: SETs with a typical charging energy of 15 K and a resistance of 100 kOmega. The oxygen pressure during junction oxidation was very low, 8*10(-4) mBar, which resulted in devices with a high cut-off frequency (up to 40 GHz). The devices were characterized at 4.2 K and at 90 mK. The noise was typical for an aluminum single-electron transistor (2.5*10(-4) e/rootHz), and the gain (dI(D)/dQ(g)) was high (54.5 nA/e). (C) 2004 American Institute of Physics.