Effect of H2 for Growing Germanium–Lead Alloys By Magnetron Sputtering Epitaxy

Abstract

Si and Ge are indirect bandgap materials, and their low light emission efficiency limits the development of silicon-based optoelectronics. Studies have shown that the introduction of Pb into Ge can make the Γ valley decrease faster than the L valley, and GePb alloys can be transformed into direct bandgap materials, thereby realizing high-efficiency luminescence of silicon-based materials. Since Pb atoms have a larger core and can provide a greater electronegativity difference for Ge, GePb alloys can be transformed into direct bandgap materials with only about 3.4% Pb. In addition, the maximum optical gain of GePb alloys is much higher than that of GeSn alloys, as revealed by first principal calculations. Therefore, the epitaxial investigation of GePb alloys is of great significance for Si photonics. In this work, Ge1- x Pb x (1.2% < x < 2.4%) alloys were grown by magnetron sputtering epitaxy using H2 and Ar mixture. The effects of different proportions of H2 and Ar on the growth of GePb were studied in detail. High crystal quality Ge0.984Pb0.016 alloys without Pb surface segregation were successfully fabricated. The results show that the increase of H2/Ar ratio contributes to the increase of Pb composition in GePb alloys. Figure 1