Controlling electric field and electron density in a double-gated GaAs/AlGaAs quantum well.

We demonstrate that the vertical electric field and the electron density of a two-dimensional electron system (2DES) can be controlled in a double-gated GaAs/AlGaAs quantum well (QW). Photoluminescence (PL) spectra from the recombination of an electron with a hole bound to a beryllium acceptor atom are measured as functions of gate biases applied to front and back gates. By comparing the measured spectra with theoretical models, we analyze the effect of the potential gradient in the QW on the PL energy for different electron filling. While a photoexcited electron recombines with a bound hole in an empty QW, a layer of 2DES is induced when the conduction band bottom of the QW lowers below the Fermi energy by the back-gate bias. In this case, a simple capacitor model gives a good estimation of the electron density. When we increase the front-gate bias, another electron layer is formed on the other side of the QW. These two electron layers screen the electric field inside the QW where the PL energy is insensitive to the gate bias. [ABSTRACT FROM AUTHOR]