The luminescence spectrum of n-i-p-i doping superlattices shows a strong, excitation dependent red shift. Time resolved measurements of the decay of the luminescence provide a valuable tool for the determination of both radiative and non-radiative lifetimes. Our results obtained from GaAs n-i-p-i crystals, grown by molecular beam epitaxy, reconfirm that recombination across the indirect gap in real space is the mechanism responsible for the luminescence. The radiative lifetime increases by more than five orders of magnitude during detectable decay, in agreement with the theoretically expected behavior.
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The authors would like to thank A. Fischer and W. Heinz for expert technical assistance. The financial support of the Bundesministerium fHr Forschung und Tech-nologie is gratefully acknowledged.
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