Electro-optical trap for dipolar excitons

An electro-optical trap for spatially indirect dipolar excitons is implemented in a GaAs/AlAs Schottky diode with a 400-$\mathring{\mathrm{A}}$-wide GaAs single quantum well. In the presence of bias voltage applied to the gate, the trap for excitons appears upon annular illumination of the structure by a continuous-wave or pulsed laser generating hot electron-hole pairs in the quantum well. A barrier for excitons collected inside the illuminated ring appears due to screening of the applied electric field by nonequilibrium charge carriers within the excitation region. Excitons are collected inside the ring due to the ambipolar drift of carriers and the dipole-dipole repulsion of excitons in the optically pumped region. For dipolar excitons thus accumulated in the middle of the ring-shaped electro-optical trap, significant narrowing of the luminescence line is observed with increasing excitation density, which indicates the collective behavior of the excitons.