(Invited) Photoluminescence Diagnostics of Nanoscale Dissolution of III-V Semiconductor Nanoheterostructures
Authors: Dubowski Jan J 
Published: May 2020

Etching of semiconducting materials with atomic level resolution is of high interest to technologies addressing the fabrication of low-dimensional devices and the tunability of their optoelectronic properties. Atomic layer etching (ALE) based on cycling between a self-limited surface reaction and selective removal of the reaction products is a promising technique addressing the challenges of controlling the variability necessary in the atomic-scale material removal [1]. However, the requirement to alter the processing hardware while completing two cycles of ALE, as well as the lack of a simple diagnostic technique for monitoring in situ material etching with a sub-monolayer resolution, have restricted the application of this technique to laboratories equipped with relatively expensive hardware infrastructures. To alleviate some of the problems of the ALE technique, we have investigated digital photo-assisted etching of GaAs/AlGaAs nanoheterostructures, which has the potential to offer a simple approach for fabrication of low-dimensional devices. The premise of this approach is based on the expectation that dark corrosion of a semiconductor is negligible in a processed solution. This is the case, for instance, for some of the III-V semiconductors immersed in deionized water or weak aqueous solutions of ammonia. The photo-ALE is an innovative method of a cycled digital photocorrosion (DIP) of semiconductors that we have explored for shallow etching of three-dimensional GaAs/AlGaAs nanoheterostructures [2, 3]. The rate and stability of DIP depends on the energy and intensity of photons employed for optical excitation of the samples, as well as on the chemistry of a liquid environment employed for processing [4]. The excitation of electron-hole pairs allows the convenient application of the photoluminescence (PL) effect for monitoring in situ of the DIP process. The DIP process can also be monitored by measuring the open circuit potential of revealed surfaces [5], which is of a particular interest to materials with negligible PL emission.
In the frame of this presentation, I will discuss some fundamental aspects of the DIP process and application of the PL effect for monitoring sub-monolayer removal of GaAs and AlGaAs. The compatibility of the photo-ALE technology with the chemistry of liquids employed for passivation of surfaces and coating with self-assembled monolayers offers the potential for in situ passivation of atomically clean surfaces. Furthermore, the sensitivity of a low-excitation intensity generated PL signal to surface defects allows spatially-resolvable recording of the perturbation of the DIP process. I will also discuss the perspective of an application of the photo-ALE to other III-V materials, as well as to Si and SiGe.
______________________
[1] K. J. Kanarik et al., "Overview of atomic layer etching in the semiconductor industry," Journal of Vacuum Science& Technology A: Vacuum, Surfaces, and Films, vol. 33, no. 2, p. 020802, 2015, doi: 10.1116/1.4913379.
[2] S. Aithal, N. Liu, and J. J. Dubowski, "Photocorrosion metrology of photoluminescence emitting GaAs/AlGaAs heterostructures," Journal of Physics D: Applied Physics, vol. 50, no. 3, p. 035106, 2017.
[3] M. R. Aziziyan, H. Sharma, and J. J. Dubowski, "Photo-Atomic Layer Etching of GaAs/AlGaAs Nanoheterostructures," Acs Appl Mater Inter, vol. 11, no. 19, pp. 17968-17978, 2019/05/15 2019, doi: 10.1021/acsami.9b02079.
[4] H. Sharma, K. Moumanis, and J. J. Dubowski, "pH-Dependent Photocorrosion of GaAs/AlGaAs Quantum Well Microstructures," The Journal of Physical Chemistry C, vol. 120, no. 45, pp. 26129-26137, 2016/11/17 2016, doi: 10.1021/acs.jpcc.6b08844.
[5]. S. Aithal and J. J. Dubowski, "Open circuit potential monitored digital photocorrosion of GaAs/AlGaAs quantum well microstructures," Appl Phys Lett, vol. 112, no. 15, p. 153102, 2018, doi: 10.1063/1.5023134.