Transformation of nonradiative recombination centers in GaAs/AlGaAs quantum well structures upon treatment in a CF4 plasma followed by low-temperature annealing

The influence of low-temperature annealing on the photoluminescence of GaAs /AlGaAs single-quantum-well structures treated in a low-energy CF4 plasma i s investigated. It is established that annealing at 160-300 degrees C cause s a decrease of the photoluminescence intensity of the quantum wells locate d in the near-surface region, while annealing at 350-450 degrees C leads to partial restoration of their photoluminescence. The activation energy for the diffusion of plasma-produced point defects and the activation energy fo r the annealing of these defects are determined. These energies are equal t o 150 and 540 meV, respectively. It is discovered that the photoluminescenc e of the quantum wells near the substrate, which had a low intensity in the as-grown sample, increases after treatment in the plasma and decreases aft er subsequent annealing monotonically with increasing annealing temperature . Repeated treatment in a CF4 plasma leads to a repeated increase in the ph otoluminescence intensity of these quantum wells. It is theorized that the defects induced by the CF4 plasma form complexes with defects introduced du ring growth and that these complexes are not recombination centers. After l ow-temperature annealing, the complexes dissociate, and the nonradiative re combination centers are recreated. (C) 1998 American Institute of Physics. [S1063-7826(98)00812- 6].