Tailoring the Optical and Structural Properties of SiGeSn by Ion Implantation

Alexander W. Henry, The University of Western Ontario

Abstract

SiGeSn compounds are tunable semiconductors offering flexibility in lattice parameters and band structure, making them promising for integrating electronic and photonic devices. Applications include lasing, waveguides, high electron mobility transistors, and fully depleted metal-oxide-semiconductor field-effect transistors. This study examined the optical and material properties of 20 - 60 nm SiGeSn layers fabricated by ion implantation on Si (001) substrates, using techniques such as Spectroscopic Ellipsometry (SE), channeling Rutherford Backscattering Spectroscopy (c-RBS), Positron Annihilation Spectroscopy (PAS), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX). RBS verified Ge and Sn implantation depth profiles and doses, and showed Ge accumulation at the SiO₂/Si interface, and peak Ge concentrations of 25–75 at.%. SE modeling, supported by RBS data, showed a ~50 nm thick implanted layer with enhanced near-IR absorption. Annealing increased Ge and Sn substitutionality with the highest values at 800°C while reducing defects. The study demonstrated that annealing improved the structural and optical properties of SiGeSn layers, particularly enhancing near-IR and short-wave-IR absorption compared to Si. Ge and Sn incorporation into the silicon lattice increased with annealing temperatures above 600°C, reducing defect densities and promoting substitutionality of Ge and Sn. Notably however, Sn clustering occurred at higher temperatures (>800°C). Optimized samples exhibited strong absorption beyond 1100 nm, attributed to high Ge and Sn incorporation, making them suitable for those optoelectronic applications in which absorption is desirable, such as detectors and photovoltaics.