SWIR-NIR Highly Absorbent Si1-xSnx Alloy Film on Si(100) Substrate: Crystal Structure, Optical Properties and Thermal Stability

Thin (200-600 nm) Si-Sn alloy films were grown under ultrahigh vacuum conditions by co-deposition of Si and Sn on the Si (100) substrate at room temperature. Investigations of the film structure by X-ray diffraction showed the preservation of the amorphous structure of Si-Sn films without the contribution of the Si1-xSnx alloy with sphalerite lattice at Sn concentration in the range of x=0.14-0.19. Analysis of optical spectra and calculations showed that an amorphous Si-Sn film with a Sn concentration of 19% is a semiconductor with indirect fundamental optical transition with very high absorption at photon energies 0.2 – 1.0 eV. It was found that precipitation of β-Sn occurs with an increase of Sn concentration up to 40%, which is accompanied by an increase in the reflection coefficient to 0.6-0.8 at photon energies below 0.8 eV. The limited temperature stability of amorphous Si-Sn films is shown for high-energy and long-term (10 minutes) laser irradiation due to the formation of metallic precipitates of β-Sn.