Effect of in-situ annealing on the structural and optical properties of GeSn films grown by MBE

This paper reports the use of in-situ thermal treatments to modify the properties of GeSn films and their performance in the infrared and Terahertz wave bands. The GeSn films were grown by molecular beam epitaxy under various conditions. X-ray analysis indicated the presence of amorphous phases and oxides in the GeSn films when they were epitaxially grown under low substrate temperature. Raman spectroscopy showed that the GeSn characteristic peak moved toward the larger wavenumber of 3.711 cm−1, and the intensity increased by 22.2% for the annealed GeSn (3.28% Sn) film. Moreover, it was determined from the full-wave reflection spectra that the direct band-gap is around 0.843 eV (1.47 μm). In-situ annealing accelerated the diffusion and ion substitution process of Sn atoms in the Ge lattice, which promoted the stability of the GeSn crystal cell and their optical performances in the infrared and terahertz range.