Micro-transfer-printed InGaAs/GaAsSb photodetectors on silicon enable broadband, high-speed optical interconnects

As communication rates continue to rise, conventional O- and C-band optical links are facing growing pressure from increasing data traffic. The 2 µm wavelength region has recently attracted attention as a promising new spectral window, supported by advances in hollow-core fiber and thulium-doped fiber amplifiers. To fully exploit this opportunity, photodetectors must combine high speed, high responsivity, broadband spectral coverage, and compatibility with silicon photonic platforms.

In this work, researchers developed an InGaAs/GaAsSb type-II superlattice photodetector that is heterogeneously integrated onto silicon using micro-transfer printing (µTP). Instead of relying on thicker absorption layers to improve responsivity, the team introduced a cavity formed by a backside Au reflector and a low-refractive-index BCB layer. This design enhances the optical field in the absorber while helping mitigate the conventional trade-off between responsivity and bandwidth.

The optimized device demonstrated broadband operation from 0.8 to 2.5 µm, covering not only the emerging 2 µm band but also conventional O- and C-band wavelengths. The cavity-enhanced structure produced a 57.9% increase in responsivity at 2 µm. The photodetector achieved responsivities of 0.85 A/W at 1.55 µm and 0.6 A/W at 2.0 µm, together with 3 dB bandwidths of 17 GHz and 18.7 GHz, respectively. Clear eye diagrams at 50 Gbps further confirmed its high-speed performance.

The study shows that µTP can serve as a practical integration route for bringing high-performance III–V photodetectors onto silicon. By combining mature III–V superlattice absorber technology with silicon-compatible heterogeneous integration, the work offers a promising platform for future optical interconnects, silicon photonic integrated circuits, and broadband optical sensing systems.