Characterization of surface nanostructures by STM light emission: individual GaAs/AlGaAs quantum wells

By spectroscopically analyzing the light emitted by specific nanostructures under the scanning tunneling microscope tip (scanning tunneling microscopy light emission spectroscopy: STM-LES), we have investigated the electronic and optical properties of individual quantum wells (QWs) of p-type AlGaAs/ GaAs layered structures. Atomic resolution was obtained on the cleaved (110 ) surface that shows the cross-sections of QWs, and the emission spectra fr om individual wells were measured by injecting electrons from the STM tip i nto them. Each individual well emits a spectrum that is consistent with the electronic transitions for the appropriate well width and also with the ph otoluminescence (PL) spectra. Furthermore, the diffusion length of minority carriers were estimated in real space by injecting electrons at different distances from a given well, and by observing the change in the emission in tensity. (C) 2000 Elsevier Science B.V. All rights reserved.