Photoluminescence study of confined donors in GaAsAlxGa1-xAs quantum wells

The photoluminescence from doped GaAs quantum wells in GaAsAlxGa1-xAs multiple-quantum-well structures has been studied at very low laser excitation intensity. Under these conditions, new impurity-associated features appear at energies both below and above that of the impurity-related transition reported in earlier work. The new feature at lower energy is attributed to transitions between electrons on neutral Si donors at the centers of the wells and confined heavy holes, while the feature reported in earlier work is attributed to confined ionized donor bound excitons and the new high-energy feature to confined neutral donor bound excitons. With this assignment, binding energies for Si donors at the centers of the wells agree with values deduced from far-infrared experiments.