TUNNELING SPECTROSCOPY OF OD STATES

We have studied tunnelling processes between a multiple quantum dot (M QD) system and a two-dimensional electron gas (2DEG) system, which are realized on a GaAs-AlGaAs-GaAs heterostructure. Using a tranfer Hamil tonian formalism it is shown that the tunnelling probability for trans itions between a zero-dimensional (0D) and a two-dimensional (2D) stat e strongly depends on the quantum dot potential profile. In the case o f a square well potential, only the resonance of the ground state is p ronounced significantly, whereas for a cosine-shaped quantum dot poten tial profile a multitude of resonance structures is caused by each 0D state. From our experimental results we concude that the potential of the quantum dots is best described by a cosine-shaped profile. In addi tion, the subband spacings and the extent of the wavefunctions of the individual subbands are also determined directly.