Standing charge density waves driven by electron drift in patterned (Al,Ga)As/GaAs heterostructures.

We have experimentally investigated the effect of electron drift on the plasma resonance of the 2-dimensional, (2D), electron gas in submicron patterned (Al,Ga)As/GaAs heterostructures. Metal gratings were deposited on the surface of modulation doped heterostructures, and alloyed into the structure providing periodic "ohmic" contacts to the 2-D electron gas. 2-D plasma resonances were measured by sub-milimeter wave transmission spectroscopy from 300 to 3000 GHz. The effect of electron drift was detected by measuring the change in high frequency conductance caused by pulsed currents applied perpendicular to the grating lines. The drifting electrons caused the plasma to either split or change frequency. The changes are an order of magnitude larger than expected from a model based on a cold classical plasma drifting under the grating. Alternatively, a standing charge density wave, induced by the current flow, can lead to either a splitting or frequency shift as seen experimentally.