We report on optically induced charge transport measurements through conducting submicron channels in AlGaAs/GaAs heterostructures. The channels are defined within a two-dimensional electron gas in a quantum well by chemical etching. By applying a voltage to a top gate, the channels can be depleted electrostatically. We present two different heterostructure designs and two processing techniques to build nanostructured optoelectronic detectors. We demonstrate the suitability of our devices for optically induced charge transport measurements in the mesoscopic regime.