The excitation-intensity dependence of photoluminescence from the tunable band gap in GaAs n-i-p-i superlattices has been studied as a function of laser frequency, and of thickness and doping concentration of the constituent layers of the superlattice. The results demonstrate that with increasing doping concentration the luminescence frequency may be tuned even over a wider range than previously reported. This increased tunability range and excitation-intensity dependence of the luminescence agrees with our theoretical expectations.
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Acknowledgements The authors are indebted to A. Fi scher and E. Schubert for expert help in sample preparation, to W. Heinz for technical assistance with the PL measurements, and to J. Lagois for a critical reading of the manuscript. Part of this work was sponsored by the Bundesministerium fur Forschung und Technology of the Federal Republic of Germany.