Optical mapping of the boundary of a two-dimensional electron gas by a nearfield optical microscopy

We constructed a dilution-refrigerator-based near-field scanning optical microscope (NSOM) which operates at temperatures down to 200 mK. Our NSOM enables us to investigate spatial properties of the electrons in semiconductor nanostructures with a subwavelength spatial resolution. We report on a result of the optical mapping of the boundary of a two-dimensional electron gas in a gated Hall-bar structure of a GaAs/AlGaAs modulation-doped single heterojuntion.