Formation of sharp potential minima close to a quantum point contact by impinging alpha particles

We report the first observation of sharp and spatially localized maxima in the density of a two-dimensional electron gas (2DEG) created by impinging alpha particles. The 5 MeV alpha particles were each found to generate a positive charge in the n+ doped AlGaAs, which in turn created the potential notch for the 2DEG at the GaAs/AlGaAs interface. This notch was found to decay logarithmically over a time scale of several seconds. The expected profile of the potential minima was roughly determined by the influence the potential had on the conductance of the nearby quantum point contact. Alpha particles hitting within about 5 mum from the point contact could be detected.