CARRIER RECOMBINATION IN A PERIODICALLY DELTA-DOPED MULTIPLE-QUANTUM-WELL STRUCTURE

We have theoretically and experimentally investigated the optical-exci tation-dependent carrier recombination lifetime in a periodically delt a-doped InGaAs/GaAs multiple-quantum-well structure. The spatial separ ation of photogenerated electrons and holes results in an increased se nsitivity to the optical excitation intensity in proportion to the inc rease in carrier lifetime. Experimentally, we find more than six order s of magnitude reduction in the carrier recombination rate over that f or spatially direct transitions under low-excitation conditions. On th e other hand, theory predicts intrinsic recombination rates for ideal structures far below those found experimentally. Various mechanisms su ch as electric-field-enhanced redistribution of the dopants during epi taxial growth, statistical variations in the separation of the dopants , and extrinsic recombination channels caused by misfit dislocations a re discussed as possible origins for this discrepancy.