High-speed Si-Ge avalanche photodiodes

Abstract

High-speed optical interconnects of data centers and high performance computers (HPC) have become the rapid development direction in the field of optical communication owing to the explosive growth of market demand. Currently, optical interconnect systems are moving towards higher capacity and integration. High-sensitivity receivers with avalanche photodiodes (APDs) are paid more attention due to the capability to enhance gain bandwidth. The impact ionization coefficient ratio is one crucial parameter for avalanche photodiode optimization, which significantly affects the excess noise and the gain bandwidth product (GBP). The development of silicon-germanium (Si-Ge) APDs are promising thanks to the low impact ionization coefficient ratio of silicon, the simple structure, and the CMOS compatible process. Separate absorption charge multiplication (SACM) structures are typically adopted in Si-Ge APDs to achieve high bandwidth and low noise. This paper reviews design and optimization in high-speed Si-Ge APDs, including advanced APD structures, APD modeling and APD receivers.

Design and Optimization of High-Responsivity High-Speed Ge/Si Avalanche Photodiode in the C+L Band

“…Since the photon propagation path of the surface-illuminated APD is in the same direction as the carrier multiplication path, there is a restrictive relationship between the responsivity and bandwidth [ 30 ]. Then three groups of different Ge absorption layer thicknesses (0.6 μm, 0.7 μm, 0.8 μm) were chosen for type 3 and type 4 to simulate the R p and 3-dB bandwidth f 3-dB , select the appropriate thickness to attain high-performance device.…”

Under-Seawater Immersion β-Ga2O3 Solar-Blind Ultraviolet Imaging Photodetector with High Photo-to-Dark Current Ratio and Fast Response

“…For PDs, the detection range and performance greatly depend on the photosensitive materials. Silicon-based photodiode is a SBUV detector commonly used in commercial applications, but its further use is hindered by the small band gap (1.1–1.3 eV) which causes a high sensitivity to infrared, visible, and near-ultraviolet. , Combined with the inevitable problems of uneven shadows and a large number of noises in imaging, , exploring another material with better characteristics is needed for the development of SBUV seawater detection. β-Ga 2 O 3 is considered as a more promising alternative because of its ultrawide band gap (which is about 4.8 eV, with an absorption cutoff edge around 280 nm, essentially suitable for SBUV detection , and narrow-band response signals.…”

Application of Graphene-Combined Rare-Earth Oxide (Sm2O3) in Solar-Blind Ultraviolet Photodetection

“…Ultraviolet (UV) light with a wavelength of 200–280 nm is called solar-blind UV light. , UV detectors applied to this band have shown superiority with their low false alarm rate, low background noise, and strong anti-interference ability. , This has made solar-blind UV detectors a research hotspot in the field of semiconductors. , …”

“…1,2 UV detectors applied to this band have shown superiority with their low false alarm rate, low background noise, and strong anti-interference ability. 3,4 This has made solar-blind UV detectors a research hotspot in the field of semiconductors. 5,6 In recent years, semiconductor materials that have been applied to UV detectors have gradually evolved from the firstgeneration ones of Si and Ge and the second-generation ones of GaAs, GaP, and InAs to the third-generation ones of SiC, GaN, and ZnO.…”