Oscillations of hopping conductance in an array of charge-tunable self-assembled quantum dots

An array of 3 x 10(7) Ge self-assembled quantum dots is embedded into the active channel of a Si metal-oxide field-effect transistor. Conductance oscillations with the gate voltage resulting from successive loading of holes into the dots are observed. On the basis of measurements of the temperature dependence of the conductance maxima, the charge-transfer mechanism in the channel is identified as being due to variable-range hopping between the dots, with the typical hopping energy determined by inter-dot Coulomb interaction. The characteristic spatial dimension of the hole wavefunctions as well as the charging energies of the dots are determined from the conductance data.