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Study on Ge/GeSn double heterojunction vertical cavity surface emitting laser enabled by ultra‐injection technique

A Ge/GeSn/Ge double heterojunction p‐i‐n vertical cavity surface emitting laser (VCSEL) is designed in this paper. According to the principle of distributed Bragg reflection (DBR), 6 and 12 pairs of SiO2/Si layers as the DBR are prepared on the upper and lower sides of the p‐i‐n structure. The upper and lower DBRs, as the resonant cavity of the laser, replace the Fabry Perot (FP) cavity of the conventional laser. The effects of Sn component and the ultra‐injection technique on the performance of the device are introduced at the same time to realize the direct bandgap luminescence of GeSn in the case of lower Sn component. The level of ultra‐injection is adjusted by changing the thickness of the i‐layer. The relationship between the thickness of the i‐layer and the carrier distribution after energization, the illuminating power, and the threshold current density are analyzed, and the best photoelectric performance is obtained.