Spatially resolved scanning tunneling luminescence on self-assembled InGaAs/GaAs quantum dots

Scanning-tunneling microscope induced luminescence at low temperature has been used to study the carrier injection into single self-assembled InGaAs/GaAs quantum dots. Electrons are injected from the tip into the dots, which are located in the intrinsic region of a p-i-n junction, and contain excess holes under typical operational conditions. Only a fraction (similar to4%) of the dots is found to be optically active under local electrical excitation. Spatial dependent measurements indicate a highly nonhomogeneous electron diffusion towards the dots. By analyzing the spatial dependence of individual peaks in the measured spectra, the contributions of individual dots to the total, multidot spectrum can be disentangled. (C) 2003 American Institute of Physics.