GATE PERFORMANCE IN RESONANT-TUNNELING SINGLE-ELECTRON TRANSISTOR

Gate performance for observing Coulomb oscillations and Coulomb diamon ds are compared for two types of gated sub-mu m double-barrier heteros tructures, Thr first type of device contains modulation-doped barriers . whereas the second type of device contains a narrower band gap mater ial for the well and no barriers with doped impurities. Both the Coulo mb oscillations and Coulomb diamonds are modified irregularly as a fun ction of ate voltage in the first type of device, while in the second type of device they are only systematically modified, reflecting atom- like properties of a quantum dot. This difference is explained in term s of the existence of Impurities in the first type of device, which in homogeneously deform the rotational symmetry of the lateral confining potential as the gate voltage is varied. The absence of impurities is the reason why we observe the atom-like properties only in th second t ype of device.