Single-electron transistor with metallic microstrips instead of tunnel junctions

A single-electron transistor (SET) comprising highly resistive Cr thin-film strips (sheet resistance ∼4 kΩ) instead of traditional tunnel barriers is reported. Two such strips (∼1 μm long) connect two Al outer electrodes to an Al island 1 μm in length equipped with a capacitively coupled gate. This transistor with a total asymptotic resistance of 110 kΩ showed a perfect Coulomb blockade and strictly e-periodic reproducible modulation by the gate in wide ranges of bias (V) and gate (Vg) voltages. In the Coulomb-blockade region (|V|⩽ about 0.5 mV), we observed a strong suppression of the transport current, allowing modulation curves V(Vg) with appreciable amplitude to be measured at a fixed bias current value I as low as 100 fA. The background-charge noise of our SET was found to be similar to that of typical Al/AlOx/Al tunnel-junction single-electron transistors, namely δQ≈5×10−4e/Hz at 10 Hz. The electron transport mechanism is discussed.