Single Photon Detector Barrier Junction for Dark Current Reduction
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Solution Overview
Problem
Single photon detectors face challenges in minimizing dark current, which leads to erroneous photon detection due to thermally generated electric charges, especially at lower temperatures where the number of thermally generated charges decreases but their lifetime increases, causing dark current to either not decrease or increase.
Innovation Solution
A single photon detector configuration that includes a buffer layer, light absorption layer, grading layer, electric field control layer, and window layer sequentially formed on a substrate, with a barrier junction formed around the active area to control the electric field and minimize dark current, and an ohmic contact layer, anode, and cathode electrodes to manage the electric field and attract dark current away from the active area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If temperature is lowered to reduce thermally generated charges, then the number of thermally generated charges decreases, but the lifetime increases and the probability of entering the SPAD active area increases, causing dark current to not decrease or increase
Solution Approach 1:
A barrier junction is introduced as an intermediary structure between the light absorption layer and the active area. This barrier junction creates a potential barrier that deflects thermally generated charges away from the active area, preventing them from causing dark current even when their lifetime is extended at lower temperatures
Solution Approach 2:
The barrier junction creates a localized region with different electrical properties (higher potential barrier) specifically around the active area perimeter. This local modification of electrical characteristics selectively affects only the charges near the active area boundary, deflecting them before they can enter and cause dark current
2Object-generated harmful factors
If a barrier junction is formed around the active area to deflect dark current, then dark current is reduced, but the device structure becomes more complex
Solution Approach 1:
The barrier junction is merged with the existing layered structure of the SPAD detector. It is formed by extending the doping region through the window layer into the light absorption layer, combining the barrier function with the existing detector architecture rather than adding a completely separate component
Solution Approach 2:
The barrier junction is formed as a ring-shaped structure that segments the detector into an inner active area and an outer region. This segmentation allows the barrier to selectively affect only charges generated in specific regions while leaving the core detection function intact
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 enhances photon detection performance by significantly reducing dark current and dark count noise, minimizing false photon detection and improving detection accuracy.
Implementation Method 1
the barrier junction may form an electric field when power is applied to the anode and a cathode electrode formed on the barrier junction
Implementation Method 2
electron-hole pairs are generated at the PN junction by photons incident on the PN junction
Implementation Method 3
The electron-hole pairs obtain energy from the strong electromagnetic field applied to the PN junction and are in turn accelerated, generating new electron-hole pairs. The cumulative occurrence of this phenomenon is called the avalanche (electron avalanche) phenomenon
Data Source
AI summary
According to an embodiment, a single photon detector configured to reduce a dark current comprises a buffer layer, a light absorption layer, a grading layer, an electric field control layer, and a window layer sequentially formed on a substrate. An active area may be formed in the window layer. A barrier junction may be formed through the window layer up to at least a portion of the light absorption layer, around the active area.