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GeSn alloys are promising for CMOS-compatible photonics and electronics, offering band‐gap engineering from SWIR to MWIR, on-chip light sources/detectors, and strain-tunable high-mobility channels. Yet, pushing Sn content high enough for direct-gap behavior remains difficult due to low Sn solubility in Ge, growth-induced compressive strain, defect generation, and a tendency to segregate or phase separate. Laser processing emerges as a versatile, maskless post-processing route that can precisely tailor the structure and electronic properties with sub-micrometre selectivity by adjusting the pulse duration and fluence.
We investigate single-pulse nanosecond treatment of epitaxial GeSn and interrogate the response with a co-registered nanoscale toolkit: AFM for relief, SCM and KPFM for local nanoelectronics, and micro-Raman mapping for strain/composition. Nanosecond pulses generate wide heat-affected halos in which electronic reconfiguration evolves away from the crater, enabling selective modulation of carrier type, band bending, and lateral depletion correlated with Raman-resolved strain/composition fields. We establish a direct, resolved linkage between structural (strain and Sn redistribution) and electronic (surface potential, carrier type, depletion) responses in GeSn under single-shot nanosecond excitation. The treatment writes robust nanoelectronic motifs: ring-like lateral junctions at the rim, tunable depletion wells, and a low-CPD annulus co-located with resolidified edges. From these observations we outline a processing–property map for nanosecond laser post-processing, in which fluence selects electronic landscape width and contrast. This positions single-pulse nanosecond irradiation as a practical maskless route to seed lateral and vertical junctions and programmable potential profiles in GeSn devices.
The work is supported by NSF EAGER 2423217 and NRFU 2023.03/0060.
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