Growth of single-crystalline GeSn films with high-Sn content on InP substrates by sputtering and rapid thermal annealing

In this work, the polycrystalline GeSn film with Sn content of 25.3 % on InP is obtained by sputtering at room temperature and then rapid thermal annealing (RTA) at 300 ℃. The single-crystalline GeSn film with Sn content of 24.7 % on InP is obtained by sputtering at 200 ℃ and then RTA at 300 ℃. This indicates that the growth temperature is one of the key factors affecting the formation of single-crystalline films. The effects of the sputtering power and film thickness on the crystallization of the GeSn films are investigated. The competition between the spontaneous and substrate-induced crystallization of the films limits the preparation of single-crystalline GeSn films. The strain relaxation of the film (R = 69.3 %) is achieved by annealing. The device fabricated by the GeSn film exhibits a high response of 18.1 A/W @-1 V at room temperature with the 1550-nm-line excitation. These suggest that sputtering epitaxy can be an effective method for growing single-crystalline GeSn films with high-Sn content on InP substrates, which is of great significance for developing high-performance mid-infrared devices.