10-Gb/s InGaAs p-i-n Photodiodes With Wide Spectral Range and Enhanced Visible Spectral Response

By selectively removing the InP cap layer on top of the conventional double-heterojunction InP-InGaAs-InP p-i-n photodiodes (PDs), a PD with high quantum efficiency in the 0.55- to 1.65-mum spectral range was realized. With antireflection coating designed both for 0.85- and 1.3-mum wavelengths, quantum efficiency higher than 80% in the 0.85- to 1.65-mum range and higher than 70% in the 0.55- to 1.65-mum range was achieved. In addition, we use a novel chip-level package technique, a self-positioned micro-ball-lens on chip, to get a large spatial alignment tolerance for the PDs. The combination of these two features significantly enhances the spectral and spatial detection range of our 10-Gb/s InGaAs p-i-n PD. Besides, exhibiting a dark current smaller than 50 pA, the PD has a 3-dB bandwidth higher than 10.3 GHz at 1.3-mum wavelength. At the 10.3-Gb/s data rate, back-to-back eye diagrams of the PD are both wide open at 0.85- and 1.3-mum wavelengths. Since both high-efficiency and high-speed operation can be achieved, receivers based on such devices are suitable for both 0.85- and 1.3-mum single-mode and multimode fiber-optic communication systems