High-Responsivity Waveguide-Integrated ${{\mathbf{G}{{\mathbf{e}}_{1 - {\bm{x}}}}\mathbf{S}{{\mathbf{n}}_{\bm{x}}}}}/{{\mathbf{Ge}}}$-Based p-i-n Photodetectors on Silicon Platform for Short-Wave Infrared Applications

This letter presents a novel approach to improve the optical responsivity by developing $\mathrm{G}{{\mathrm{e}}_{1 - x}}\mathrm{S}{{\mathrm{n}}_x}/\text{Ge}$ waveguide-integrated p-i-n photodetectors (WGPDs) on the silicon (Si) platform. The proposed WGPD demonstrates an absorbance of ∼99%, which is 50% greater than the absorbance shown by the conventional p-i-n PD. In addition, the WG core's height and the PD's length significantly impact the optical evanescent field. Specifically, when the WG core height is increased, it results in a decrease in responsivity. On the other hand, increasing the PD length leads to increased responsivity. As a result of optimizing the WG core height and PD length, the WGPD achieves an unprecedented level of responsivity at a wavelength of 1.55 µm. The responsivity at a wavelength of 1.55 µm is >1.97A/W, surpassing the performance of both conventional p-i-n PD and previously theoretically reported values. It is remarkable to note that this value of responsivity is the highest theoretical value to date. Therefore, the proposed $\mathrm{G}{{\mathrm{e}}_{1 - x}}\mathrm{S}{{\mathrm{n}}_x}/\text{Ge}$ -on-Si WGPD presents a promising opportunity for developing high-performance optical receivers in short-wave infrared (SWIR) bands.