Tunnelling spectroscopy of 0D states

We have studied tunnelling processes between a multiple quantum dot (MQD) system and a two-dimensional electron gas (2DEG) system, which are realized on a GaAs-AlGaAs-GaAs heterostructure. Using a transfer Hamiltonian formalism. It is shown that the tunnelling probability for transitions between a zero-dimensional (0D) and a two-dimensional (2D) state strongly depends on the quantum dot potential profile. In the case of a square well potential, only the resonance of the ground state is pronounced significantly, whereas for a cosine-shaped quantum dot potential profile a multitude of resonance structures is caused by each 0D state. From our experimental results we conclude that the potential of the quantum dots is best described by a cosine-shaped profile. In addition, the subband spacings and the extent of the wavefunctions of the individual subbands are also determined directly.