Single-Photon Detector With Multiple Avalanche Layers
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Solution Overview
Problem
Existing single-photon avalanche diodes face challenges in achieving high photon detection efficiency, low dark count rate, low afterpulsing probability, and narrow timing response, particularly as the thickness of the multiplication layer increases, leading to worsened afterpulsing and timing jitter.
Innovation Solution
A single-photon detector with multiple avalanche layers is designed, where the overall thickness of the M-layers is split into a first and a second M-layer, with effective breakdown occurring only in the 300 nm second M-layer, suppressing afterpulsing probability and dark count rate while maintaining high gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of multiplication layer is increased to achieve high gain, then photon detection efficiency is improved, but afterpulsing probability and timing jitter worsen
Solution Approach 1:
The multiplication layer is divided into multiple sub-layers (first multiplication layer, second multiplication layer, third multiplication layer) with different thicknesses and doping characteristics. This segmentation allows each sub-layer to contribute differently to gain generation while controlling the overall afterpulsing effect, resolving the contradiction between achieving high gain and minimizing afterpulsing probability.
Solution Approach 2:
Different regions of the multiplication layer are designed with different local properties: the first multiplication layer has specific doping concentration and thickness optimized for initial gain, while subsequent layers have adjusted parameters to maintain gain while reducing carrier multiplication that causes afterpulsing. This local optimization enables high overall gain with suppressed afterpulsing probability.
2Reliability
If the thickness of multiplication layer is increased to achieve high gain, then photon detection efficiency is improved, but timing response widens
Solution Approach 1:
The multiplication layer is segmented into multiple thin sub-layers rather than one thick layer. This segmentation reduces the total transit time for carriers through the multiplication region while maintaining the cumulative gain effect, thereby improving timing response speed without sacrificing photon detection efficiency.
Solution Approach 2:
Instead of increasing gain by extending the multiplication layer in one dimension (thickness), the patent uses multiple layers stacked in series, transforming the single-thickness approach into a multi-layer dimensional structure. This allows gain to be accumulated across layers while keeping each layer thin for fast carrier transit and narrow timing response.
3Reliability
If the thickness of multiplication layer is increased to achieve high gain, then photon detection efficiency is improved, but device speed deteriorates
Solution Approach 1:
The multiplication layer is divided into multiple thin sub-layers with optimized individual thicknesses. This segmentation enables high cumulative gain across all layers while maintaining short carrier transit distances in each layer, preventing speed deterioration that would occur with a single thick multiplication layer.
Solution Approach 2:
The patent optimizes multiple parameters including doping concentrations, layer thicknesses, and material compositions across different multiplication layers. By carefully adjusting these parameters, the device achieves high gain for improved photon detection efficiency while maintaining fast response speed through optimized carrier multiplication and transit characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively improves the performance of single-photon detectors by reducing afterpulsing probability and dark count rate, maintaining low timing jitter, and preventing speed deterioration, making it suitable for applications like photon-counting and photon-timing.
Implementation Method 1
Near infrared single-photon avalanche diode (SPAD) has shown its potential and capability of time-of-flight (ToF) measurement and faint light detection
Data Source
AI summary
A single-photon detector is provided. The detector has multiple avalanche layers. It has an avalanche photodiode (APD) structure using single photon. The APD is made of indium aluminum arsenide (InAlAs). At least two avalanche layers are designed. When the layer for avalanche is numbered only one and the gain is very big, the speed will be deteriorated very quickly. With the design of two avalanche layers in the present invention for the very big gain, the speed deterioration can be suppressed. After measuring, the present invention shows a faster speed as compared to prior arts. It proves that, by using more than two avalanche layers, the present invention effectively improves the feature of single-photon detector. Hence, the present invention is especially suitable for single-photon detection.