Polycrystalline GeSn thin films fabricated by simultaneous laser sintering and recrystallization

The photodetectors for mid-infrared (IR) applications mainly depend on HgCdTe, PbS, and PbSe materials. The mid-IR photodetectors can be achieved through GeSn alloy. In this paper, we demonstrated a new method for the polycrystalline GeSn thin films deposition on the silicon substrate. The simultaneous laser sintering (LS) of nanoparticles and recrystallization is demonstrated to be effective for fabricating smooth and consistent films. The GeSn films were fabricated with 2 and 12% Sn atomic ratios. The thickness of the deposited films was around 4 µm. Results are presented for both quasi-continuous wave IR laser and nanosecond pulsed ultraviolet laser. The polycrystalline GeSn films of about 2.5 µm thickness with 12% Sn were attained using the LS process. The GeSn thin films with a 12% atomic Sn ratio showed a Raman peak at 295 cm −1 after the LS process. The added Sn causes a left shift of 5 cm −1 from the standard Ge–Ge peak. The polycrystalline GeSn alloy formation was identified by the X-Ray diffraction 2 θ peaks of GeSn (111), (220), (311), and (400) at an angle of 27.15°, 44.10°, 53.71°, and 64.8°, respectively. The GeSn films with 12% atomic Sn concentration showed high hole mobility of 240 cm 2 /V⋅s. The films can absorb around 70% of the incident near-IR to mid-IR light. The proposed LS process is highly effective for faster polycrystalline GeSn film growth. It also removes surface porosity and voids from the films and increases adhesion with the substrate. Additionally, this LS process is scalable to different atomic Sn ratios.