Abstract
In this work, we demonstrate In0.52Al0.48As top/backside-illuminated avalanche photodiodes (APD) with dual multiplication layers for high-speed and wide dynamic range performances. Our fabricated top-illuminated APDs, with a partially depleted p-type In0.53Ga0.47As absorber layer and thin In0.52Al0.48As dual multiplication (M-) layer (60 and 88 nm), exhibit a wide optical-to-electrical bandwidth (16 GHz) with high responsivity (2.5 A/W) under strong light illumination (around 1 mW). The measured bias dependent 3-dB O-E bandwidth was pinned at 16 GHz without any serious degradation near the saturation current output. To further increase the speed, we downscaled the active diameter and adopted a back-side illuminated structure with flip-chip bonding for batter optical alignment tolerance. A significant improvement in maximum bandwidth was demonstrated (25 versus 18 GHz). On the other hand, we adopted a thick dual M-layer (200 and 300 nm) and 2 μm absorber layer in the APD design to circumvent the problem of serious bandwidth degradation under high gain (>100) and high-power operation which significantly enhanced the dynamic range. Due to dual M-layer, the carriers could be energized in the first M-layer then propagate to the second M-layer to trigger the avalanche process. In both cases, despite variation in thickness of the absorber and M-layer, the cascade avalanche process leads to values close to the ultra-high gain bandwidth product (GBP) of around 460 GHz with a responsivity of 0.4 and 1 A/W at unit gain for the thin and thick M-layer devices, respectively. We successfully achieved a good sensitivity of around −20.6 dBm optical modulation amplitude (OMA) at a data rate of 25.78 Gb/s, by packaging the fabricated APDs (thin dual M-layer (60 and 88 nm) version) with a 25 Gb/s trans-impedance amplifier in a 100 Gb/s ROSA package. The results show that, the incorporation of a dual multiplication (M) layer structure in the APD opens a new window to obtaining the higher GBP in order to meet the requirements for high-speed transmission without the need of further downscaling the multiplication layer.
Highlights
Introduction distributed under the terms andThe swift growth in the capacity of communication networks has led to new services, such as mobile broadband for smart devices, social networking, cloud computing, and online streaming
Significant research has been done on possible alternative materials like silicon-germanium (Si/Ge) and the III-V compounds, such as InP, InGaAs, and InAlAs, for the fabrication of high-speed avalanche photodiodes (APD) for high data rate applications [2]
By varying the thickness of the hybrid absorber layer, we can boost the speed of an APD for a given responsivity and vice versa
Summary
The swift growth in the capacity of communication networks has led to new services, such as mobile broadband for smart devices, social networking, cloud computing, and online streaming. In order to meet the requirements for high-speed transmission, a lot of effort has been made to improve the bandwidth and gain bandwidth product (GBP). There are various factors limiting the speed, gain, and noise in the receiver performance in high-speed systems, for instance, the avalanche build-up time, which depends on the material and the thickness of the avalanche layer. APD (Device B) design with thick absorber and dual M-layers, there is a relaxation in the trade-off between the avalanche gain and the bandwidth. 1.25 GHz with a responsivity as high as 33 A/W at 0.9 Vbr can be achieved using a device with a large optical window diameter (200 μm). Photonics 2021, 8, 98 absorber layer to obtain a higher GBP, in order to meet the requirements of high‐speed transmission Such APDs with high GBP and high responsivity and a large.
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