Design and Analysis of Separate-Absorption-Transport-Charge-Multiplication Traveling-Wave Avalanche Photodetectors

Abstract

This paper proposes a novel type of avalanche photodiode-the separate-absorption-transport-charge-multiplication (SATCM) avalanche photodiode (APD). The novel design of photoabsorption and multiplication layers of APDs can avoid the photoabsorption layer breakdown and hole-transport problems, exhibit low operation voltage, and achieve ultra-high-gain bandwidth product performances. To achieve low excess noise and ultra-high-speed performance in the fiber communication regime (1.3 1.55 m), the simulated APD is Si-based with an SiGe-Si superlattice (SL) as the photoabsorption layer and traveling-wave geometric structures. The frequency response is simulated by means of a photo-distributed current model, which includes all the bandwidth-limiting factors, such as the dispersion of microwave propagation loss, velocity mismatch, boundary reflection, and multiplication/transport of photogenerated carriers. By properly choosing the thicknesses of the transport and multiplication layers, microwave propagation effects in the traveling-wave structure can be minimized without increasing the operation voltage significantly. A near 30-Gb/s electrical bandwidth and 10 avalanche gain can be achieved simultaneously, even with a long device absorption length (150 m) and low operation voltage ( 12 V). In addition, the ultrahigh output saturation power bandwidth product of this simulated TWAPD structure can also be expected due to the large photoabsorption volume and superior microwave-guiding structure. Index Terms-Avalanche photodetector, avalanche photodiode (APD), high gain-bandwidth-product avalanche photodetector, high-saturation-power photodetector, Si-SiGe-based photodetector, Si-SiGe-based superlattice (SL), traveling-wave photodetector, ultra-high-speed photodetector. I. INTRODUCTIONT HE rapid growth in Internet traffic has created an urgent need to increase the channel bandwidth capacity of fiber-optic communication systems. As a key component in these transmission systems, ultra-high-speed photodetectors are able to not only increase the transmission capability in a single channel, but also reduce the required number of channels and complexity of management in a wavelength-division-multiplexing (WDM) fiber communication system [1]. There

Avalanche Photodiodes with Dual Multiplication Layers for High-Speed and Wide Dynamic Range Performances

“…This absorption layer thickness and the ratio of p-type/intrinsic layer thickness were chosen to balance the resistance-capacitance (RC) and transit time limited bandwidth [1]. We conducted an APD bandwidth simulation based on our proposed linear model, which included the bandwidth limiting factors of the avalanche delay time, secondary hole transit time, and RC-delay time [18]. For sensitivity measurement, samples of device C with both the top-and back-side illuminated structures were fabricated.…”

High-power and high-responsivity photodiode for long-haul and short-reach fiber communication

“…Figure 10(a) and 10(b) shows the conceptual band diagram and top-view of fabricated device, respectively. We adopted the structure of traveling-wave photodiode [21] to realize our device for high bandwidth-efficiency product performance. As shown in Figure 10(b), the ridge optical waveguide structure can also minimize the long-tail problem, which is originated from the substrate photocurrent [1,[6][7][8], due to the confinement of optical power in the surface epi-layers.…”

“…The p-type doped profile and thin thickness of the barrier and well (33Å) of the Si 0.5 Ge 0.5 /Si SL can minimize the hole-trapping problem in traditional Si/SiGe multiple quantum well (MQW). We adopted such p-doped SL and a depleted Si layer to construct our photo-absorption region, which is similar to the structure of a p-i-n photodiode with partially p-doped photo-absorption region for high saturation power performance [2,21]. On the other hand, the trade-off between carrier multiplication time and RC bandwidth limitation, which is originated from the large device capacitance of a thin multiplication layer (150nm) and the carrier multiplication time, can be released due to the existence of this additional depleted Si layer [21].…”

Si ∕ Si Ge -based edge-coupled photodiode with partially p-doped photoabsorption layer for high responsivity and high-power performance

“…Figures 1͑a͒ and 1͑b͒ show the conceptual band diagram and top view of the fabricated device, respectively. We adopted the structure of a traveling-wave photodiode 11 to realize our device for high bandwidth-efficiency product performance. As shown in Fig.…”

“…12,13 We, thus, adopted p-doped SL and a depleted Si layer to construct our photoabsorption region, which is similar to the structure of a p-i-n photodiode with a partially p-doped photoabsorption region, 14 for the purpose of achieving high saturation power 14 and releasing the RC bandwidth limitation due to the thin multiplication layer ͑150 nm͒ in our structure. 11 The epitaxial layer structures were grown through ultrahigh vacuum/chemical vapor deposition ͑UHV/CVD͒ on an n + -doped Si substrate. We fabricated the demonstrated device by using the standard photolithography, metallization, liftoff, and dry etching processes.…”