Single-electron transistor with metallic microstrips instead of tunnel junctions

A single-electron transistor (SET) comprising highly resistive Cr thin-film strips (sheet resistance similar to4 k Omega) instead of traditional tunne l barriers is reported. Two such strips (similar to1 mum long) connect two Al outer electrodes to an Al island 1 mum in length equipped with a capacit ively coupled gate. This transistor with a total asymptotic resistance of 1 10 k Omega showed a perfect Coulomb blockade and strictly e-periodic reprod ucible modulation by the gate in wide ranges of bias (V) and gate (V-g) vol tages. In the Coulomb-blockade region (\V\less than or equal to about 0.5 m V), we observed a strong suppression of the transport current, allowing mod ulation curves V(V-g) with appreciable amplitude to be measured at a fixed bias current value I as low as 100 fA. The background-charge noise of our S ET was found to be similar to that of typical Al/AlOx/Al tunnel-junction si ngle-electron transistors, namely deltaQ approximate to 5x10(-4)e/root Hz a t 10 Hz. The electron transport mechanism is discussed. (C) 2001 American I nstitute of Physics.