Transport properties of quantum dots with steep walls - art. no. 125309

Quantum dots are fabricated in a Ga[Al]As heterostructure by local oxidatio n with an atomic force microscope. This technique, in combination with top gate voltages, allows us to generate small lateral depletion lengths. The c onfinement is characterized by low-temperature magnetotransport measurement s, from which the dots energy spectrum is reconstructed. We find that in sm all dots the addition spectrum can qualitatively be described within a Fock -Darwin model. For a quantitative analysis, however, a steep-wall confineme nt has to he considered. In large dots with small lateral depletion length, our measurements indicate that the density of states within Landau level 2 inside the dot is larger than that within Landau level 1, an effect that w e interpret in terms of steep walls. Furthermore, we demonstrate that our i nterpretation is consistent within the charge-density model. The maximum wa ll steepness achieved is of the order of 0.4 meV/nm.