High-Speed and Broadband InGaAs/InP Photodiode with InGaAsP Graded Bandgap Layers

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This study presents the development of a high-speed, broadband InGaAs/InP photodiode suitable for advanced sensing and optical detection applications across the critical wavelength range of 850-1550 nm. By employing an InAlAs window layer to replace conventional InP, the device significantly improves sensitivity at 850 nm. Additionally, the substitution of traditional GaAs-based materials with InGaAs enhances responsivity and reduces carrier transit times, enabling precise, high-speed signal detection. The introduction of InGaAsP graded bandgap layers (GBLs) further improves device reliability and reduces absorption losses associated with defects, thus enhancing overall sensing performance. The fabricated photodiode, featuring an active area diameter of 35 µm, achieves high bandwidths of 20 GHz, 15 GHz, and 15.5 GHz at 850 nm, 1310 nm, and 1550 nm, respectively, along with responsivities of 0.5 A/W, 0.72 A/W, and 0.64 A/W. These characteristics make the device well suited for integration into multi-wavelength optical sensing systems, broadband photonic sensors, and high-speed optical communication platforms.