Photodiode Structure with Localized Impurity Zones for Dark Current Reduction
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Solution Overview
Problem
Existing photodetectors for weak light detection face challenges in minimizing dark current, which can be exacerbated by surface depletion and edge breakdown, affecting the separability and sensitivity of pixel detection.
Innovation Solution
A photodiode structure is designed with a p− type semiconductor layer, n+ type semiconductor regions, and a p type semiconductor region, where the n+ type semiconductor regions have higher impurity concentrations and smaller areas to minimize dark current, and the avalanche multiplication region is optimized between the n+ and p type semiconductor regions to enhance photon detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If surface depletion is prevented to suppress surface dark current, then dark current is reduced, but pixel separability is weakened
Solution Approach 1:
The patent applies local quality by creating different impurity concentration zones within the semiconductor layer. Specifically, it forms a first semiconductor region with higher impurity concentration than the surrounding semiconductor layer, while maintaining a second semiconductor region with lower impurity concentration. This local differentiation allows the high impurity concentration region to suppress surface dark current through reduced surface depletion, while the low impurity concentration region maintains adequate pixel separability and prevents edge breakdown.
2Strength
If the region between p+ type semiconductor layer and separating part is made p− type to suppress edge breakdown, then edge breakdown is suppressed, but dark current increases due to wide area depletion layer formation
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through spatially differentiated impurity concentrations. Instead of making the entire region between the p+ type semiconductor layer and separating part uniformly p− type, the invention creates a localized first semiconductor region with higher impurity concentration where edge breakdown occurs. This localized high impurity concentration suppresses edge breakdown without forming a wide area depletion layer, thereby preventing dark current increase while maintaining edge breakdown suppression.
3Measurement precision
If avalanche multiplication is enhanced for weak light detection, then detection sensitivity is improved, but dark current multiplication is also enhanced
Solution Approach 1:
The patent addresses this contradiction through local quality by confining the avalanche multiplication function to a specific first semiconductor region with higher impurity concentration, while maintaining a separate second semiconductor region with lower impurity concentration. The high impurity concentration in the first region enables effective avalanche multiplication for weak light detection, while the low impurity concentration in the second region minimizes dark current generation and multiplication. This spatial separation of functions allows sensitivity enhancement without proportional dark current increase.
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 configuration reduces dark current noise and improves the signal-to-noise ratio, enabling high-sensitive photodetectors with low dark current levels, thereby enhancing the detection of weak light signals.
Implementation Method 1
a photodiode that multiplies a charge generated by photoelectric conversion in an avalanche region
Implementation Method 2
An APD is a photodiode that multiplies signal charge generated by photoelectric conversion using avalanche breakdown to enhance detection sensitivity
Data Source
AI summary
A photodiode that multiplies a charge generated by photoelectric conversion in an avalanche region includes: a p− type semiconductor layer having interfaces; an n+ type semiconductor region located inside the p− type semiconductor layer and in contact with the interface; an n+ type semiconductor region located inside the p− type semiconductor layer and connected to the n+ type semiconductor region; and a p type semiconductor region located between the n+ type semiconductor region and the interface, wherein the n+ type semiconductor region, the n+ type semiconductor region, and the p type semiconductor region each have a higher impurity concentration than the p− type semiconductor layer, the avalanche region is a region between the n+ type semiconductor region and the p type semiconductor region inside the p− type semiconductor layer, and the n+ type semiconductor region has a smaller area than the n+ type semiconductor region in planar view.