Probing the potential landscape inside a two-dimensional electron Gas

We report direct observations of the scattering potentials in a two-dimensional electron gas using electron-beam diffraction experiments. The diffracting objects are local density fluctuations caused by spatial and charge-state distribution of donors in the GaAs-(Al,Ga)As heterostructures. The scatterers can be manipulated externally by sample illumination or by cooling the sample down under depleted conditions.