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arXiv · 2304.11097

In-situ study and modeling of the reaction kinetics during molecular beam epitaxy of GeO2 and its etching by Ge

Wenshan Chen·Kingsley Egbo·Hans Tornatzky·Manfred Ramsteiner·Markus R. Wagner·Oliver Bierwagen
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Abstract

Rutile GeO2 has been predicted to be an ultra-wide bandgap semiconductor suitable for future power electronics devices while quartz-like GeO2 shows piezoelectric properties. To explore these crystalline phases for application and fundamental materials investigations, molecular beam epitaxy (MBE) is a well-suited thin film growth technique. In this study, we investigate the reaction kinetics of GeO2 during plasma-assisted MBE using elemental Ge and plasma-activated oxygen fluxes. The growth rate as a function of oxygen flux is measured in-situ by laser reflectometry at different growth temperatures. A flux of the suboxide GeO desorbing off the growth surface is identified and quantified in-situ by the line-of-sight quadrupole mass spectrometry. Our measurements reveal that the suboxide formation and desorption limits the growth rate under metal-rich or high temperature growth conditions, and leads to etching of the grown GeO2 layer under Ge flux in the absence of oxygen. The quantitative results fit the sub-compound mediated reaction model, indicating the intermediate formation of the suboxide at the growth front. This model is further utilized to delineate the GeO2-growth window in terms of oxygen-flux and substrate temperature. Our study can serve as a guidance for the thin film synthesis of GeO2 and defect-free mesa etching in future GeO2-device processing.

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Wenshan Chen, Kingsley Egbo, Hans Tornatzky, Manfred Ramsteiner, Markus R. Wagner, Oliver Bierwagen. 2023-04-21. In-situ study and modeling of the reaction kinetics during molecular beam epitaxy of GeO2 and its etching by Ge. https://doi.org/10.1063/5.0155869

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