Photodetector Blocking Zone Reduces Dark Current
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Solution Overview
Problem
Conventional photodetectors face challenges in reducing parasitic currents and electricity consumption, particularly in low-light intensity conditions, due to high noise levels and inefficient blocking of charge carriers.
Innovation Solution
A photodetector design featuring a blocking zone with a higher conduction band level than the absorbing zone to prevent majority charge carrier passage, combined with additional blocking zones and quantum wells to effectively block minority carriers, reducing dark current and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional photodiode with p-n junction is used, then the device structure is simple, but the parasitic current (dark current) is high
Solution Approach 1:
The photodetector is divided into multiple functional zones: an absorbing zone for light detection, a blocking zone to prevent carrier diffusion, and a contact zone for electrical connection. This segmentation isolates the harmful diffusion current in the blocking zone while preserving light detection in the absorbing zone, thereby reducing overall parasitic current without significantly increasing structural complexity.
Solution Approach 2:
A blocking zone is introduced as an intermediary layer between the absorbing zone and the contact zone. This blocking zone, with its higher conduction band level, acts as a barrier that mediates the interaction between photogenerated carriers and the contact, preventing direct diffusion of majority carriers and reducing dark current.
2Object-generated harmful factors
If cooling is applied to reduce diffusion current, then the diffusion current is reduced, but the operating temperature decreases and cooling system requirements increase
Solution Approach 1:
The blocking zone with its higher conduction band level is designed to exploit the natural energy barrier to block majority carriers. Instead of relying on cooling to reduce thermal excitation, the structure converts the potential harm of thermal energy into a beneficial effect by using the conduction band offset to prevent carrier diffusion, thereby reducing dark current without requiring temperature reduction.
3Object-generated harmful factors
If a blocking zone with higher conduction band level is introduced, then majority carrier passage is prevented, but the device complexity increases
Solution Approach 1:
The blocking zone is designed with specific local properties: it is doped with a doping concentration different from the absorbing zone, and it has a higher conduction band level. These localized quality changes are confined to the blocking zone only, allowing the rest of the device to maintain simpler characteristics while achieving the carrier blocking function where needed.
4Object-generated harmful factors
If additional blocking zones and quantum wells are added to block minority carriers, then dark current is further reduced, but the device complexity increases
Solution Approach 1:
The blocking zone is designed to contain nested structures including quantum wells and additional blocking zones within it. This nested arrangement allows multiple functions (minority carrier blocking, potential well formation, field modulation) to be integrated within a single zone, reducing the need for separate external structures and managing complexity through hierarchical organization.
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 significantly reduces parasitic currents and electricity consumption, improving the quality of the image formed and allowing operation at higher temperatures with equivalent image quality, thus reducing cooling system requirements and increasing the photodetector's operability and reliability.
Implementation Method 1
a blocking zone (3) which opposes the passage of majority charge carriers between the contact zone (2) and the absorbing zone (1), characterized in that the blocking zone (3) has a higher conduction band level than the absorbing zone (1) so as to prevent the passage of majority charge carriers
Implementation Method 2
The absorbing zone 1 is configured to absorb light radiation in a first wavelength range
Data Source
Figure 1~5
Figure 6~10
AI summary
The invention relates to a photodetector which includes an absorbing area (1) made up of a first semiconductor material having a first band gap energy value. It also includes a blocking area (3e, 3c) made up of at least second and third semiconductor materials configured to prevent the passage of the majority charge carriers between the absorbing area (1) and a contact area (2e, 2c), the second semiconductor material having a second band gap energy value higher than the first band gap energy value in order to form a quantum well with the third semiconductor material. The blocking area (3e, 3c) is doped.