Infrared Detector Cooling with Forward Bias Carrier Injection
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Solution Overview
Problem
Cooled photodetectors in infrared detectors often exhibit atypical behavior and excessive noise due to electrically active traps, leading to reduced performance and false alarms, with existing solutions like factory calibration being impractical in many applications.
Innovation Solution
Applying a forward bias during the temperature lowering process of the photodetector, allowing majority carriers to pass through and potentially fill or recombine trapped carriers, thereby reducing the number of atypical pixels and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is performed to exclude outlier pixels, then measurement precision is improved, but device complexity and operational constraints increase
Solution Approach 1:
The patent applies preliminary action by performing carrier injection during the cooling process before the photodetector reaches its operating temperature. This fills electron traps in advance, preventing them from causing noise and atypical behavior during subsequent operation, thereby eliminating the need for complex post-manufacturing calibration processes.
2Object-generated harmful factors
If photodetector temperature is lowered to operating temperature, then noise from electrically active traps is reduced, but atypical behavior persists due to trapped carriers
Solution Approach 1:
The patent converts the harmful effect of electron traps into a beneficial process. By injecting carriers during cooling, the traps that would normally cause noise and atypical behavior are instead filled with carriers, transforming them from harmful defects into a mechanism that improves pixel reliability and reduces noise during operation.
3Reliability
If forward bias is applied during temperature lowering, then carrier injection fills electron traps reducing atypical behavior, but additional control circuitry is required
Solution Approach 1:
The patent merges the cooling process with the carrier injection process. The forward bias is applied specifically during the temperature lowering phase, combining two operations (cooling and trap filling) into a single integrated process, which minimizes additional complexity while maximizing the benefit of reduced atypical pixel behavior.
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 method effectively reduces the probability of atypical behavior and noise in photodetectors, allowing for improved performance and increased operational frequencies, particularly effective at temperatures below -73°C.
Implementation Method 1
lowering the temperature of the photodetector... the photodetector sees its temperature drop from a first temperature which is, for example, the ambient temperature to a second temperature, for example, its working temperature
Implementation Method 2
During this lowering of temperature, or during at least part of this lowering of temperature, the photodetector is forward biased. This forward bias results in the passage of a current of majority carriers through the photodetector
Data Source
Figure 1~2
AI summary
In an infrared detector equipped with a photodiode (1), when the photodiode's temperature is lowered to its operating temperature, the photodiode (1) is forward-biased. During this forward biasing, a majority carrier current is injected through the photodiode (1). These majority carriers mask some of the photodiode's defects. The acquisition phase is then performed by reverse-biasing the photodiode (1).