Buffer-Free Ge/Si by Rapid Melting Growth Technique for Separate Absorption and Multiplication Avalanche Photodetectors

Herein, we report the formation of buffer-free germanium (Ge) on silicon by a two-step rapid melting growth technique for separate absorption and multiplication (SAM) avalanche photodetectors (APDs) as well as its characteristic measurements. The quality of the Ge film was verified by standard electron microscopy and Raman spectroscopy. The high-quality Ge functioned as the absorption layer, whereas the multiplication layer was made with the Si layer. The electrical measurement identified that the photodetector shows high responsivity and gain to the near-infrared spectrum before the breakdown. The nanocrystallites and the intermixing SiGe layer at the interface will be the recombination centers for the photogenerated electron-hole pairs, resulting in a low photocurrent in a low-bias range. This letter demonstrated that buffer-free Ge films and SAM APDs with good photoelectric conversion efficiency would be obtained using a CMOS-compatible process.