Sequential and cotunneling behavior in the temperature-dependent thermopower of few-electron quantum dots

We have studied the temperature-dependent thermopower of gate-defined, lateral quantum dots in the Coulomb blockade regime using an electron heating technique. The line shape of the thermopower oscillations depends strongly on the contributing tunneling processes. Between 1.50.3em0exK and 400.3em0exmK a crossover from a pure sawtooth to an intermittent sawtoothlike line shape is observed. The latter is attributed to the increasing dominance of cotunneling processes in the Coulomb blockade regime at low temperatures.