PECVD Growth of Composition Graded SiGeSn Thin Films as Novel Approach to Limit Tin Segregation

SiGeSn is a promising group IV material to develop the field of silicon photonics. Increasing the tin concentration in the alloy is desired in order to achieve a direct bandgap in the material. This necessitates low temperature growth and proper strain management in the films during growth to prevent tin segregation. In this work, plasma enhanced chemical vapor deposition (PECVD) was used to grow composition graded SiGeSn films at low processing temperatures of 350 degrees C-380 degrees C using a simplified PECVD reactor. Polycrystalline films were deposited using a multi-step approach to prevent tin phase separation at higher Sn concentrations by alleviating the strain arising from the incorporation of Sn in the film lattice. Rutherford Back Scattering measurements indicated that films with Sn content of up to 8% without any Sn phase segregation were achieved. The structural and optical properties of the films were analyzed using X-ray diffraction and Raman spectroscopy. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.