Atomic-scale analysis of quantum nanostructures with the STM

Important features of semiconductor quantum structures can be observed by cross-sectional scanning tunneling microscopy down to the atomic scale. The MBE-grown III-V multilayers are cleaved in UHV to expose an atomically flat cross-sectional plane, which is then imaged with the STM. Chemically selective imaging enables us to distinguish between atoms within the group III and analyze the AlGaAs composition in atomic detail: we find Al clustering on the scale of a few nanometers in many MBE-grown materials. The heterojunction interfaces and their roughness can be analyzed down to the unit-cell lattice period. The electronic signature of active dopants such as Be is observed and quantified. Recent work shows that all these possibilities can be used to study the MBE growth of AlAs/GaAs superlattices on V-grooved substrates with unprecedented detail. © 1995 Elsevier Science B.V. All rights reserved.