Fig. 1. (Color online) (a) Schematic cross-section of the Si/graded-SiGe/Ge/Ge_0.9Sn_0.1 p–i–n photodetector. The mesa size is 32 µm in diameter. (b) Schematic of epitaxial growth and layer transfer technique for this p–i–n structure fabrication.

Fig. 2. (Color online) Simulation of spectral responsivity of the p–i–n photodetector with single material as active region for (a) Si, (b) graded-SiGe, (c) Ge, and (d) Ge_0.9Sn_0.1.

Fig. 3. (Color online) (a) AES of the sample annealed at 800 °C for 30 min and 900 °C for 0 s. (b) AES of the sample annealed at 800 °C for 30 min and 900 °C for 10 min. (c) Schematic cross-section of the single material p–i–n photodetector. The mesa size is 32 µm in diameter. (d) Influence of SRV on dark current density of Ge p–i–n photodetector.

Fig. 4. (Color online) Simulation of J_dark of the p–i–n photodetector with single material for (a) Si, (b) graded-SiGe, (c) Ge, and (d) Ge_0.9Sn_0.1.

Fig. 5. (Color online) The variation of responsivity under different active region is simulated for (a) Ge_0.9Sn_0.1, (b) Ge, (c) Si, and (d) graded-SiGe.

Fig. 6. (a) Magnitude of the J_dark at different thickness of Ge_0.9Sn_0.1 layer. (b) The final spectral response of the designed photodetector and the J_dark changes between 0–6 V reverse bias.

Table 1. Parameters of Si, SiGe, Ge, and Ge_0.9Sn_0.1.