BINDING-ENERGY OF BOUND EXCITONS (DX)-X-0 IN QUANTUM-WELLS

The binding energies of excitons bound to silicon donors in GaAs/Ga1-x AlxAs quantum-well (QW) structures have previously been investigated e xperimentally as a function of the well width by several groups, The m ost comprehensive data show a clear maximum for a well width of about 100 Angstrom, and a steady decrease for widths above this. Existing th eories give qualitative agreement with the decrease in binding energy with increasing well width. However, no theory predicts a maximum near 100 Angstrom. Furthermore, the quantitative agreement is poor for all well widths. We develop a theoretical model using a density-functiona l approach which correctly predicts the maximum in the binding energy at 100 Angstrom. The agreement with the experimental results is signif icantly better for all well widths than that of existing models. Photo luminescence experiments have also been carried out on samples with a wide range of different doping profiles in order to clarify the previo us experimental results and provide additional information on the effe ct of the position of the impurity in the QW. [S0163-1829(98)05036-X].