Abstract
Germanium-Tin (GeSn) alloys have emerged as a promising material for future optoelectronics, energy harvesting and nanoelectronics owing to their direct bandgap and compatibility with existing Si-based electronics. Yet, their metastability poses significant challenges calling for in-depth investigations of their thermal behavior. With this perspective, this work addresses the interdiffusion processes throughout thermal annealing of pseudomorphic GeSn binary and SiGeSn ternary alloys. In both systems, the initially pseudomorphic layers are relaxed upon annealing exclusively via thermally induced diffusional mass transfer of Sn. Systematic post-growth annealing experiments reveal enhanced Sn and Si diffusion regimes that manifest at temperatures below 600{\deg}C. The amplified low-temperature diffusion and the observation of only subtle differences between binary and ternary hint at the unique metastability of the Si-Ge-Sn material system as the most important driving force for phase separation.
Highlights
The Si-Ge-Sn semiconductor system has sparked a great deal of interest among scientists because of its unique properties within group IV materials
We investigate the diffusion and lattice relaxation of both pseudomorphic GeSn binary and SiGeSn ternary alloys upon thermal annealing, to identify the behavior of each one of those systems and reveal possible differences between them
Annealing of the samples for 30 min at temperatures below 450 °C does not have a distinct effect on the layer strain, which is consistent with thermal stability data on alloys with similar composition [11]
Summary
The Si-Ge-Sn semiconductor system has sparked a great deal of interest among scientists because of its unique properties within group IV materials. The demonstrated fundamental direct band gap of this truly silicon-compatible material can pave the way for numerous new applications in the field of opto- and nanoelectronics [1]. One of the main challenges posed by (Si)GeSn alloys is maintaining their structural integrity during thermal treatment in order to preserve their intrinsic material properties. Thermal budget must be kept low enough to avoid Sn diffusion out of the material and associated segregation [8]. This physical process yields a phase separation with the GeSn equilibrium phase at a Sn content well below the critical value for a direct band gap, rendering it unsuitable for light-emitting devices. Thermally activated interdiffusion processes can smear out the interfaces and
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