Temperature range for re-emission of carriers in GaAs/Ga1-xAlxAs superlattices

The photoluminescence from n-type doped GaAs/Ga0.57Al0.43As single quantum well (QW) and GaAs/Ga0.54Al0.46As superlattice (SL) heterostructures grown by molecular beam epitaxy was studied in the temperature range 10 < T < 300 K. The temperature dependence of the QW emission energy follows the band-g ap shrinkage of bulk GaAs. The integrated intensity observed under indirect excitation of the GaAs/Ga1-xAlxAs SL drops exponentially by three orders o f magnitude above 30 K, with an activation energy of 139 meV in the range 2 5-45 K, 305 meV in the range 75-160 K and 578 meV in the range 200-300 K. T hese energies are comparable to the effective barrier height of a light-hol e, of an electron and of electron-hole pairs, respectively. The decrease of the integrated intensity is therefore attributed to thermal re-emission of confined carriers out of the QW. Near room temperature, the decrease of th e integrated intensity is because of the thermally activated nonradiative r ecombination. (C) 1999 Elsevier Science Ltd. All rights reserved.