Tunneling spectroscopy of a quantum dot through a single impurity

A single impurity inside a resonant tunneling diode is used to perform tunneling spectroscopy on an adjacent electrostatically defined vertical quantum dot. This results in tunneling between two zero-dimensional systems, measured as a set of sharp peaks in the current-voltage spectrum for finite bias. Magnetic-field-dependent measurements show that the angular momentum of the tunneling electrons is conserved during the tunneling process. Both ground and excited states are probed. The effect of temperature is also investigated, exhibiting a peak broadening that is smaller than 1 kT.