Probing the infrared properties of a p-doped Ge0.938Sn0.062 thin film via polarization-dependent FTIR spectroscopy

Abstract

The complex relative permittivity of doped Ge1−xSnx thin films (realized using state-of-the-art growth techniques) are obtained by devising a methodology based upon polarization-dependent reflection measurements along with multi-layer Fresnel reflection equations. The developed approach is implemented to acquire the complex relative permittivity of a 170-nm-thick Ge1−xSnx film exhibiting a hole carrier concentration of 3.3 × 1019 cm−3 and x = 6.2%, with this Sn composition suggesting the film is on the cusp of exhibiting a direct bandgap. The investigation conducted on this thin film as well as the developed methodology are expected to further establish Ge1−xSnx as the primary semiconductor for on-chip light emission and sensing devices.