The effects of Coulomb blockade are studied in many normal tunnel junctions connected in series. Such a structure is a natural way for creating the small capacitance necessary for Coulomb blockade. The amplitude of single-electron tunneling oscillations is exponentionally small at high temperature and is proportional to the number of junctions. The resistance of a voltage-biased superlattice at high temperature has an activated temperature dependence. The activation energy goes to zero at some threshold voltage proportional to the number of the junctions.

• Received 26 June 1989

DOI:https://doi.org/10.1103/PhysRevB.41.138