Carrier recombination in a periodically δ-doped multiple quantum well structure

We have theoretically and experimentally investigated the optical-excitation-dependent carrier recombination lifetime in a periodically δ-doped InGaAs/GaAs multiple-quantum-well structure. The spatial separation of photogenerated electrons and holes results in an increased sensitivity to the optical excitation intensity in proportion to the increase in carrier lifetime. Experimentally, we find more than six orders of magnitude reduction in the carrier recombination rate over that for spatially direct transitions under low-excitation conditions. On the other hand, theory predicts intrinsic recombination rates for ideal structures far below those found experimentally. Various mechanisms such as electric-field-enhanced redistribution of the dopants during epitaxial growth, statistical variations in the separation of the dopants, and extrinsic recombination channels caused by misfit dislocations are discussed as possible origins for this discrepancy