Propagation length of mesoscopic photocurrents in a two-dimensional electron gas

We investigate the average propagation length of photogenerated nonequilibrium electrons in a two-dimensional electron gas using a quantum point contact as a local photocurrent detector. To this end, electrons are photogenerated both quasiresonantly and nonresonantly to the optical interband transition in the quantum well comprising the two-dimensional electron gas. The photocurrent is analyzed as a function of the distance between the excitation spot in the two-dimensional electron gas and the detector. We find that the determined propagation length depends nonmonotonically on the laser intensity. We interpret the observation by an interplay of an enlarged scattering phase space of the photogenerated electrons and the screening of sample specific scatterers.