Radiative Recombination in Free Standing Quantum Boxes
We report photoluminescence measurements made on free standing lattice matched GaAs/AlGaAs and pseudomorphic InGaAs/GaAs quantum boxes fabricated by laterally patterning quantum wells using electron beam lithography and either reactive ion etching or ion beam milling. At temperatures below 20K the luminescence efficiency of the GaAs quantum box arrays tends to scale with the volume of quantum well material remaining after processing even for the smallest boxes which have lateral dimensions of only 40–50 nm. These observations suggest that the surface recombination rate in GaAs sub-micron structures is not necessarily large relative to the radiative recombination rate at low temperatures. In contrast radiative recombination in the InGaAs/GaAs quantum boxes is strongly quenched for lateral dimensions less than 500 nm. We suggest that this is because photoexcited carriers rapidly thermalise and become laterally localised in the GaAs boxes by potentials of order a few meV, perhaps arising from the effects of interface fluctuations or strain relaxation, and that such localisation effects are smaller in the InGaAs boxes.
KeywordsTitanium Methane Anisotropy Argon Recombination
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