TUNNELING AND RELAXATION OF PHOTOGENERATED CARRIERS IN NEAR-SURFACE QUANTUM-WELLS

It is shown that photoluminescence emission from AlGaAs/GaAs and InGaAs/GaAs near-surface quantum wells can be a nonlinear function of the excitation-power density depending on the surface-barrier thickness and on the conditions of the barrier-oxide interface. By studying the rate-equation system, it is shown that this nonlinear effect is mainly due to the competition between tunneling to surface states and relaxation of photogenerated carriers within the quantum well. The information about surface states that one can obtain from this nonlinear behavior is also discussed.