SPECTROSCOPY OF THE SINGLE-PARTICLE STATES OF A QUANTUM-DOT MOLECULE

We investigate low-temperature transport through two identical vertica lly coupled quantum dots in a triple-barrier heterostructure. The curr ent-voltage curve exhibits two series of current steps of different ma gnitude. On the basis of magnetotunneling measurements, we relate the current steps to the single-particle levels of a quantum-dot molecule. From the absence of many-particle phenomena, an upper limit of 1 ns i s determined for the energy-relaxation time in the double-dot system.