Silicon-Germanium Avalanche Receivers With fJ/bit Energy Consumption

Abstract

Fast, low-noise and sensitive avalanche photoreceivers are needed for surging short-reach photonic applications. Limitations concerning bandwidth, throughput and energy consumption should be overcome. In this work, we comprehensively study the performance opportunities provided by avalanche p-i-n photodetectors with lateral silicongermanium-silicon heterojunctions. Our aim is to circumvent the need for chip-bonded electronic amplifiers. In particular, we demonstrate that avalanche photodetectors based on silicongermanium-silicon heterostructures yield reliable opto-electrical performances, with high gain-bandwidth products up to 480 GHz and low effective ionization ratios down to 0.15. Moreover, they improve power sensitivities for high-speed optical signals and have a low energy dissipation of only a few fJ per received information bit. These results pave the way for high-performing receivers for energy-aware data links, in next-generation shortdistance data communications. IndexTerms-Group-IV semiconductors; Integrated photonics; Avalanche photodetectors; Energy consumption; Short-reach communications; CMOS technology I. INTRODUCTIONHE relentless demands of data-hungry devices as in data centers [1], high-performance computers and servers [2] or big data clouds and storages [3] places exponential requirements on electrical wire signaling. Data overflow in metal wires is a critical bottleneck that hampers the take-off of such devices. The benefits of optical interconnects extend from long-distance to short-distance systems. Components used in long-haul systems are too costly and complex to be adopted in short-reach systems, however. Short-reach architectures comprise opto-electrical and electro-optical Manuscript received MAY 31, 2021.

High-speed Si-Ge avalanche photodiodes

“…SACM APDs can realize high GBP and low excess noise but require accurate control of the doping profile in SACM structure, including layer thicknesses (or silicon charge and multiplication widths for lateral SACM APDs) and doping levels. By contrast, lateral pi-n APDs with double heterojunctions are an alternative for APD design [79,80,116]. Zhang et al proposed an APD with a lateral p-i-n junction, as shown in Fig.…”

“…The study [79]; c Schematic cross section of the waveguide-coupled Si-Ge p-i-n APD. Insets are cross-sectional views of the p-i-n device and the injection waveguide [80]; d Schematic of the p-i-n APD with lateral p-i-n heterojunctions, optical mode profiles of p-i-n APDs with various germanium widths, and light propagation through p-i-n APDs with various germanium lengths [116] of the APD multiplication gain versus the bias voltage under different input powers indicates that the multiplication gain increases with the decrease of the input optical power. The phenomenon also occurs in other types of APDs.…”

“…To study the effect of germanium geometry on device performance, Benedikovic et al investigated a lateral p-i-n APD with various germanium widths and lengths, as shown in Fig. 11(d) [116]. High GBP up to 480 GHz and low k value down to 0.15 were achieved for APD with 0.3 μm width of germanium.…”

Reconfigurable Activation Functions in Integrated Optical Neural Networks

“…In our case, we are working on the thermal noise dominated regime (low incident optical power) so there is a benefit in using APD. High-speed and low noise APD have been reported in silicon foundry compatible systems [61]. Another alternative is the use of non-invasive detectors [62] which will eliminate the necessity to take a portion of the incoming light to trigger the self-made modulation.…”

High-Performance Waveguide-Integrated Ge/Si Avalanche Photodetector with Lateral Multiplication Region

“…Near-infrared photodetectors have been widely used in fiber communication [ 1 , 2 , 3 , 4 , 5 ], spectroscopy [ 6 , 7 ], and light detection and ranging (LIDAR) [ 8 , 9 ]. High-speed and high-sensitivity photodetectors are desirable to relax the power budget and improve the energy efficiency of fiber communication.…”