High-speed InGaAs/GaAsSb type-II superlattice avalanche photodiodes beyond 2 µm.

The 2 μm spectral window has emerged as a promising candidate to mitigate the impending capacity crunch of the standard C-band. However, the development of high-speed photodetectors, specifically avalanche photodiodes (APDs), remains a bottleneck compared to the maturity of 2 μm fiber and amplifier technologies. In this paper, we report on a high-speed surface-illuminated APD operating at 2 μm, grown on an InP substrate with an InGaAs/GaAsSb type-II superlattice (T2SL) absorption layer. The device exhibits an extended cutoff wavelength exceeding 2.4 μm. The responsivity is measured to be 0.14 A/W at unity gain under illumination from a 2 μm laser. A 3-dB bandwidth of 10.2 GHz is achieved for a 20-μm diameter device. Furthermore, clear open eye diagrams are demonstrated at data rates up to 15 Gb/s.