(Invited) Photoluminescence Monitored Digital Photocorrosion of GaAs/AlGaAs Nanoheterostructures

Abstract

Conventional etching techniques do not have the ability to achieve precision of monolayer etching of crystalline solid materials. In recent years, atomic layer etching (ALE) has emerged as a method addressing this challenge based on the application of self-limiting sequential reactions. Nevertheless, monitoring of the ALE process, important for real time information about the location of the etching front, is not trivial and could be an expensive task. We have investigated the innovative process of digital photocorrosion (DIP) of GaAs/AlGaAs nanoheterostructures, which is based on photoexcitation driven decomposition of these materials.1 The process is carried out in a flow cell filled with etchants designed for selective removal of the photocorrosion products. For instance, water dilutes relatively easily As and most of the Ga oxides, but dilution of Ga2O3 or Al oxides and hydroxides requires dedicated etchants. Under optimized conditions, DIP allows etching of (001) GaAs/AlGaAs nanoheterostructures with average rates approaching 1 Å/cycle. The process could be monitored in situ by measuring, e.g., open circuit potential2 or photoluminescence3 effect. The sensitivity of these effects to the surface states of a semiconductor allows for convenient marking of the location of a GaAs/AlGaAs interface when crossed by the etching front.In this presentation, I will discuss mechanisms of DIP of GaAs/AlGaAs nanoheterostructures and the conditions for formation of stoichiometric surfaces. Examples of the DIP process applied for formation of an unusual density alkanethiol self-assembled monolayers and operation of optical devices for detecting electrically charged molecules immobilized in the vicinity of a semiconductor-electrolyte interface will also be discussed. Finally, I will also address the potential of this economically attractive invention for the research of other semiconductor materials.__________________1. S. Aithal, N. Liu and J. J. Dubowski, Journal of Physics D: Applied Physics 50 (3), 035106 (2017).2. S. Aithal and J. J. Dubowski, Appl Phys Lett 112 (15), 153102 (2018).3. M. R. Aziziyan, H. Sharma and J. J. Dubowski, Acs Appl Mater Inter 11 (19), 17968-17978 (2019).