Lateral variation of the electron density across a Hall bar in high electric and magnetic fields

A two-dimensional electron gas is studied in the presence of strong electric and magnetic fields by spatially resolved photoluminescence spectroscopy. By an analysis of the emission spectrum, we find a strong variation of the electron density across the Hall bar. In the high-field limit the optical response changes from essentially excitonlike to plasmalike within a few micrometers across the Hall bar. The observed phenomenon is assigned to an electrostatic interaction between the semiconductor surface and the two-dimensional electron gas, which is caused by the Hall field generated across the two-dimensional electron gas.