Exciton saturation in electrically biased quantum wells

We have measured the heavy hole excitation saturation intensity in GaAs/AlGaAs quantum wells as a function of applied electric field and AlGaAs barrier design. We find that the saturation intensity increased with increasing applied field, and decreasing barrier thickness or height, because of increased carrier sweep-out rates. Time-resolved sweep-out time and temperature-dependent saturation intensity measurement point out the roles of both thermionic emission and tunneling in the field and barrier-dependent carrier escape time. By reducing the barrier Al composition from 30 to 20%, we achieved an increase in the saturation intensity by a factor of ∼6.