Photoluminescence spectra of gated undoped quantum well with lateral potential modulation in low electron density

We measured the photoluminescence (PL) of a GaAs quantum well (QW) with a lateral potential modulation by the front-gate bias while changing both the electron density and electric field at low temperature. Near the onset of the two-dimensional electron gas, we observed an anomalous enhancement of PL intensity of the neutral exciton X 0 accompanied by a decrease in the intensity of the charged exciton X - . The sample was a 20-nm GaAs back-gate undoped QW with semi-transparent square-mesh surface gates. By comparing the results with those for a flat transparent surface gate sample we discuss the origin of this anomalous phenomenon. We present a possible explanation for this phenomenon, which is attributed to lateral drift motion of the X 0 in a laterally modulated exciton potential.