Phase evolution of Te-hyperdoped Si upon furnace annealing.

[Display omitted] • The microstructural evolution and phase transformation of Te-hyperdoped Si layers upon isochronal furnace annealing are investigated. • A new Raman peak (at 143.7 ± 1.4 cm−1) emerges for Te-hyperdoped Si layers annealed at 950 °C and above. • Te-rich crystalline clusters with a hexagonal shape are assigned to Si 2 Te 3 via TEM and polarization Raman analysis. • Positron annihilation lifetime spectroscopy suggests the formation of vacancy complexes upon furnace annealing. Si hyperdoped with chalcogens via ion implantation and pulsed laser melting is known to exhibit strong room-temperature sub-bandgap photoresponse. As a thermodynamically metastable system, an impairment of the optoelectronic properties in hyperdoped Si materials occurs upon subsequent high-temperature thermal treatment (>500 °C). The substitutional Te atoms that cause the sub-bandgap absorption are removed from the Si matrix to form Te-related complexes, which are electrically and optically inactive. In this work, we explore the formation of defects in Te-hyperdoped Si layers which leads to the electrical deactivation upon furnace annealing through the analysis of optical and microstructural properties as well as positron annihilation lifetime spectroscopy. Particularly, Te-rich clusters are observed in samples thermally annealed at temperature reaching 950 °C and above. Combined with polarized Raman analysis and transmission electron microscopy, the observed crystalline clusters are suggested to be Si 2 Te 3. [ABSTRACT FROM AUTHOR]