Effect of the electromagnetic environment on the single electron transistor

The influence of envirommental impedances on tunneling rates in a single electron transistor circuit is investigated. Effects of the finite gate capacitance and of stray capacitances at the tunnel junctions are considered. For the case of a low impedance environment the electron tunneling rates reduce to the so-called global rule rate while for a high impedance environment a modification of the so-called local rule rate arises from the stray capacitances. Special emphasis is given to the dependence of the current on the gate voltage which determines the sensitivity of electrometers based on the transistor setup. It is found that a higher sensitivity of the electrometer can be achieved by means of asymmetric transistors.