EXCITATION OF 3-DIMENSIONAL QUANTUM DOTS

Arrays of field-effect-confined quantum dots with diameters down to 10 0 nm have been prepared from AlxGa1-xAs-GaAs heterostructures. In far- infrared spectroscopy, transitions are induced between the 2-3-meV sep arated quantum levels of the lateral confinement. In tilted magnetic f ields we observe a resonant coupling to states arising from the confin ement in the growth direction. The level spacing in this z direction i s found to be only a few meV in our samples and thus comparable to the lateral confinement. We observe in tilted magnetic fields that the ex citation spectrum is determined by the total magnetic field B. Thus th e quantum dots are essentially three-dimensional objects.