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Avalanche photodiodes with multiple multiplication layers for coherent detection
Zohauddin Ahmad1, Po-Shun Wang1, Naseem1
1Department of Electrical Engineering, National Central University, Taoyuan, 320, Taiwan.
Scientific Reports
|October 3, 2022
Summary
We developed a new avalanche photodiode (APD) design using triple multiplication layers that improves both responsivity and saturation current for coherent systems. This novel APD design enhances signal-to-noise ratio in LiDAR applications and requires less optical power.
Area of Science:
- Optoelectronics
- Semiconductor Devices
- Photonics
Background:
- Coherent optical systems require high-performance photodetectors to balance responsivity and saturation current.
- Existing avalanche photodiode (APD) designs face limitations in simultaneously optimizing these critical parameters.
- Space-charge screening and device heating impact APD performance at high photocurrents.
Purpose of the Study:
- To demonstrate a novel APD design that overcomes the trade-off between responsivity and saturation current.
- To enhance receiver performance in coherent optical systems, particularly for applications like FMCW LiDAR.
- To achieve superior signal-to-noise ratio and image quality with reduced optical local-oscillator power.
Main Methods:
- Designed and fabricated a triple In$_{0.52}$Al$_{0.48}$As multiplication (M-) layer APD with a stepped electric (E-) field.
- Investigated the avalanche process and electric field distribution within the novel M-layer structure.
- Characterized device performance, including breakdown voltage, responsivity, gain, saturation current, and O-E bandwidth, comparing it to a dual M-layer reference.
Main Results:
- The triple M-layer APD exhibited lower punch-through and breakdown voltages, higher responsivity (19.6 A/W vs. 13.5 A/W), and higher maximum gain (230 vs. 130) compared to the dual M-layer.
- Achieved significantly higher 1-dB saturation current (> 5.6 mA vs. 2.5 mA) at 0.95 V$_{br}$ and extremely high saturation current (> 14.6 mA) with a 200 µm active window.
- In a coherent FMCW LiDAR test bed, the novel APD demonstrated a superior signal-to-noise ratio and 3-D image quality, requiring substantially less optical local-oscillator power (0.5 mW vs. 4 mW).
Conclusions:
- The novel triple M-layer APD design effectively relaxes the responsivity-saturation current trade-off, enabling enhanced performance in coherent systems.
- Reduced electric field in active layers leads to less space-charge screening and device heating, crucial for high photocurrent operation.
- This APD technology offers significant advantages for LiDAR and other demanding optical sensing applications, improving performance while reducing power requirements.
