High-performance p + -InGaAs/i-InGaAs/n + -Si photodetector achieved by low-quality crystalline Ge interlayer wafer bonding

In this study, we present a high-quality bonded InGaAs/Si heterojunction fabricated by a low-quality crystalline germanium (LC-Ge) interlayer wafer bonding technique. This approach effectively isolates the lattices of the InGaAs and Si materials, enabling the formation of a defect-free heterojunction interface that significantly enhances carrier transport efficiency. The fabricated InGaAs/Si PIN photodetectors exhibit a notably low dark current density of 0.24 mA/cm² under a reverse bias of –2 V, along with a near-unity ideality factor of 1.09. Moreover, a high responsivity of 0.75 A/W is achieved at a wavelength of 1550 nm. Notably, the device achieves a 3-dB bandwidth of up to 24 GHz, highlighting the effectiveness of the Ge intermediate layer in mitigating lattice and thermal mismatch issues. These results position the device as a promising candidate for advanced InGaAs/Si PIN photodetector applications.