Temperature range for re-emission of carriers in GaAs/Ga 1− xAl xAs superlattices

Abstract

The photoluminescence from n-type doped GaAs/Ga 0.57Al 0.43As single quantum well (QW) and GaAs/Ga 0.54Al 0.46As 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-gap shrinkage of bulk GaAs. The integrated intensity observed under indirect excitation of the GaAs/Ga 1− x Al x As SL drops exponentially by three orders of magnitude above 30 K, with an activation energy of 139 meV in the range 25–45 K, 305 meV in the range 75–160 K and 578 meV in the range 200–300 K. These energies are comparable to the effective barrier height of a light-hole, 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 the integrated intensity is because of the thermally activated nonradiative recombination.