HgCdTe Infrared Detector Baking to Reverse Bias Defect Damage
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Solution Overview
Problem
Mid-wave infrared detectors degrade due to high temperature operation under reverse bias, leading to increased noise and dark current, necessitating a method to improve their performance.
Innovation Solution
A method involving placing a mid-wave infrared detector in an opaque environmental chamber with controlled temperature (60-70°C) and humidity (99-99.999% nitrogen) for 72-240 hours, connected in a short circuit configuration, to bake the detector and measure pre- and post-bake noise and dark current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the detector operates at high temperature under reverse bias, then the detector can detect infrared radiation, but noise and dark current increase due to defect generation
Solution Approach 1:
The patent applies parameter changes by modifying the electrical bias configuration from reverse bias to short circuit during the baking process. This parameter change allows the detector to be heated to high temperatures (60-70°C) without generating defects, as the short circuit configuration prevents the high-temperature reverse bias condition that causes defect generation. The baking process then restores performance by removing existing defects while maintaining the short circuit configuration throughout the process.
2Reliability
If the detector is baked at high temperature to restore performance, then noise and dark current decrease, but the baking process requires precise temperature and time control
Solution Approach 1:
The patent specifies precise parameter ranges for the baking process: temperature of 60-70°C and duration of 72-240 hours. These parameter changes are optimized to restore detector performance while managing the complexity of the baking process. The short circuit configuration is maintained throughout the baking process, simplifying the control requirements compared to attempting to control reverse bias conditions at high temperatures.
3Reliability
If the detector is exposed to high temperature for extended period, then defect generation is reduced, but the baking time increases
Solution Approach 1:
The patent establishes an optimal baking time range of 72 to 240 hours at temperatures of 60-70°C. This parameter optimization balances the need for sufficient baking time to restore detector performance with the desire to minimize the total baking duration. The short circuit configuration enables this optimized time range by preventing defect generation during the baking process, whereas reverse bias would require shorter times to avoid excessive defect generation.
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
The baking process effectively reduces noise and dark current, enhancing the detector's performance by stabilizing the device's operational parameters.
Implementation Method 1
heating the environmental chamber to a bake temperature selected in the range of 60 to 70 degrees Celsius
Implementation Method 2
connecting the anode to the cathode in a short circuit configuration
Data Source
AI summary
A method of baking a detector, the method comprising: placing a mid-wave infrared detector in an environmental chamber, wherein the environmental chamber is opaque. The mid-wave infrared detector comprises an anode, a guard terminal, and a cathode. The method further comprising connecting the anode to the cathode in a short circuit configuration, heating the environmental chamber to a bake temperature selected in the range of 60 to 70 degrees Celsius, and maintaining the detector in the environmental chamber for a period selected in the range of 72 hours to 240 hours.