The motion of free electrons moving parallel and above a semiconductor surface can be influenced by shining laser light onto the surface. Here we report strong deflection of aloof electrons by an undoped GaAs surface illuminated with a 633nm laser. The deflecting electric field from the surface photovoltaic charges extends 100 { \mu}m into the vacuum. As surface photovoltage (SPV) is sensitive to the electronic states of the GaAs surface, the aloof electron beam serves as a probe for SPV charge dynamics at the mesoscopic length scale. The observed in-plane SPV charge distribution persists beyond 1 second after the laser beam is blocked. Our work suggests the possibility of writing designed 2D charge patterns on semiconductor surfaces with a scanning laser beam, providing unusual flexibility for electron beam manipulation.
Categories: quant-ph