Semiconductor Quantum Dots: Dopant versus Free Carrier Profiles

Semiconducting quantum dots (QDs) can be used to enhance the performance of a variety of devices encompassing optoelectronic, thermoelectric, and alternative energy technologies. Often, heterovalent dopants are added to the semiconducting QDs to provide extra electrons and improve conductivity. Since each QD is expected to contain fewer than 10 dopants, both the extra electrons and their “parent” dopants have been difficult to locate. In an earlier study of InAs/GaAs QDs using scanning thermoelectric microscopy,¹ fewer electrons were observed within the interior of the QD than in the surrounding substrate, presumably due to a preference of the dopant to stay outside of the QDs. In this work, we are investigating the locations of the extra electrons and their parent donors using a combination of experimental and computational methods, namely local-electrode atom-probe tomography and self-consistent Schrödinger-Poisson simulations based on effective mass theory. A comprehensive description of the relative preferences of the (parent) dopants and extra electrons with respect to the QDs and surrounding substrate will be provided.
1. J.C. Walrath, Y.-H. Lin, S. Huang, R.S. Goldman, Appl. Phys. Lett. 106, 192101 (2015).