Seed-Driven Stepwise Crystallization (SDSC) for Growing Rutile GeO2 Films via MOCVD

TL;DR

This paper introduces a seed-driven stepwise crystallization method for growing high-quality rutile GeO2 films via MOCVD, overcoming phase segregation issues and achieving full coverage and improved crystalline quality.

Contribution

The study presents a novel SDSC growth approach with sequential deposition steps that significantly enhances film coverage and quality of rutile GeO2 films.

Findings

Achieved 100% crystalline coverage of r-GeO2 films.

Reduced FWHM of X-ray diffraction by ~30%.

Demonstrated effective overcoming of phase segregation.

Abstract

Germanium dioxide (r-GeO2) is an emerging new ultrawide bandgap (UWBG) semiconductor with significant potential for power electronics, thanks to its large-size substrate compatibility and ambipolar doping capability. However, phase segregation during metal-organic chemical vapor deposition (MOCVD) on substrates like r-TiO2 has posed a significant barrier to achieving high-quality films. Conventional optimization of growth parameters has been found so far not very insufficient in film coverage and film quality. To address this, a seed-driven stepwise crystallization (SDSC) growth approach was employed in this study, featuring multiple sequential deposition steps on a pre-templated substrate enriched with r-GeO2 seeds. The process began with an initial 180-minute deposition to establish r-GeO2 nucleation seeds, followed by a sequence of shorter deposition steps (90, 60, 60, 60, 60, and 60 minutes). This stepwise growth strategy progressively increased the crystalline coverage to 57.4%, 77.49%, 79.73%, 93.27%, 99.17%, and ultimately 100%. Concurrently, the crystalline quality improved substantially, evidenced by a ~30% reduction in the Full Width at Half Maximum (FWHM) of X-ray diffraction rocking curves. These findings demonstrate the potential of the SDSC approach for overcoming phase segregation and achieving high-quality, large-area r-GeO2 films.