EFFECT OF INTERFACE ROUGHNESS ON EXCITONIC LINEWIDTH IN A QUANTUM-WELL - GOLDEN-RULE AND SELF-CONSISTENT-BORN-APPROXIMATION CALCULATIONS

We have derived expressions for the linewidth of excitons in a quantum well in the presence of interface roughness scattering, by using the Fermi golden rule and also by introducing the self-consistent Born approximation (SCBA). The fluctuation in the well width is assumed to have a Gaussian auto-correlation and is characterized by a height DELTA and a correlation length LAMBDA. The linewidth obtained from the golden rule depends on (DELTA-LAMBDA)2 and changes as L-6 with well width L. The SCBA expression is proportional to DELTA, shows a weak dependence on LAMBDA, and varies as L-3. It also agrees with the expression obtained under a statistical-fluctuation model. The calculated results of the linewidth for a GaAsAlxGa1-xAs quantum well under the golden rule are quite high, while the SCBA results are closer to the experimental data.