Theory of donor-acceptor-pair luminescence in δ-dopingn-i-p-isuperlattices

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Abstract
We investigate the pair recombination and intralayer relaxation processes in δ-doping n-i-p-i structures after a pulse excitation. The decay of the occupation probability of the impurities as well as the pure pair recombination spectra (neglecting Coulomb broadening due to other ionized impurities) as a function of time are calculated analytically. The effects of Coulomb broadening are included using two different models. In one case, the positions of charged impurities are assumed to be uncorrelated. In the second model, the correlation effect due to in-plane hopping processes occurring in parallel with the recombination is taken into account. The kinetics of the hopping relaxation is studied by a Monte Carlo simulation. Our results demonstrate that the introduction of a fixed minimum donor-acceptor-pair distance d leads to dramatic changes in the recombination kinetics and to extremely narrow luminescence spectra compared to bulk semiconductor structures of a similar doping level. This proves that this type of structure is a unique tool for the investigation of two-dimensional impurity bands. At the same time, the distance d provides an additional parameter, which allows us to optimize the experimental conditions.