Atomistic models of interface structures of GaAs-Al xGa 1− xAs ( x = 0.2−1) quantum wells grown by interrupted and uninterrupted MBE

Abstract

Atomic-scale models of heterointerface structures of GaAs-Al x Ga 1− x As quantum wells (QWs) are presented. For QWs with x > 0.5, top (AlGaAs-on-GaAs) interfaces formed by continuous MBE have the roughness of one atomic layer height whose atomic step interval is 200 Å, resulting in a well-known photoluminescence (PL) broadening from QWs. This roughness can be smoothed by growth interruption for tens of second prior to the formation of top interfaces, leading to a drastic sharpening of the PL spectra by a factor of 4–5. In contrast, bottom (GaAs-on-AlGaAs) interfaces have atomic steps of 40 Å in width irrespective of growth interruption; this step interval is so small as compared with excition size that they act as a “pseudo-smooth” interface. For QWs with x < 0.3, however, the bottom interfaces become similar to the top interface, and can be smoothed by growth interruption.