MBE growth of ultra-thin GeSn film with high Sn content and its infrared/terahertz properties

Ultra-thin GeSn films with high Sn contents were epitaxial grown on single silicon substrates with different substrate temperatures by MBE method. It is found that the GeSn film with substrate temperature lower than 450 °C still represents amorphous or partially amorphous, which might lead to a volatile optical properties or I-V curve in infrared and terahertz bands. XRD measurement shows stronger GeSn single crystal peak (400) and narrower full width at half maximum (FWHM) when increase the substrate temperature during the growth. Mid and far infrared (FT-IR) test suggests that the transmission of the GeSn films get improved for about 46% when the substrate temperature increases from 200 to 450 °C. Terahertz transmission of the GeSn samples also improved with a maximum rising rate of 25%/50 °C as the substrate temperature increases. This study of GeSn substrate temperature during the growth demonstrates it is one of the key factors to control the structure stability of the GeSn films and their infrared and terahertz properties.