QWIP Infrared Detector Doping Compensation for Carrier Saturation
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Solution Overview
Problem
Infrared detectors using quantum well infrared photodetectors (QWIPs) face sensitivity saturation issues due to increased re-trapping of carriers with more stacked barrier and quantum well layers, limiting their sensitivity enhancement potential.
Innovation Solution
The design incorporates a substrate with a lower contact layer, a first and second light receiving layer with quantum well structures, each having a specific doping configuration to optimize carrier generation and flow, including a p-type intermediate layer to compensate n-type impurities, thereby maintaining high sensitivity without saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of stacked barrier layers and quantum well layers is increased to enhance sensitivity, then the number of carriers is increased, but carriers re-trapped in the quantum well layers are also increased, causing sensitivity saturation
Solution Approach 1:
The patent applies different doping types to different regions of the quantum well structure. Specifically, the first semiconductor layer is doped with a first conductivity-type impurity while the second semiconductor layer is doped with a second conductivity-type impurity that compensates the first. This local differentiation of doping characteristics creates balanced carrier generation and extraction regions, preventing carrier re-trapping while maintaining high sensitivity even with increased stacking layers.
2Measurement precision
If Mercury cadmium tellurium (MCT) is used for high sensitivity and low noise, then detection performance is improved, but the material is highly toxic and chemically unstable, causing low yield
Solution Approach 1:
The patent fundamentally changes the material composition parameters by replacing toxic MCT with non-toxic semiconductor materials such as GaAs and InP. This parameter change maintains the quantum well structure's photoelectric conversion capability while eliminating toxicity and chemical instability issues, thereby improving manufacturing yield and ease of fabrication without sacrificing detection performance.
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 improves the signal-to-noise ratio of the detector by ensuring balanced current flow through both light receiving layers, enhancing sensitivity and maintaining high performance without saturating the detector.
Implementation Method 1
QWIP performs photoelectric conversion by optical absorption between sub-bands in the quantum well layers
Implementation Method 2
QWIP performs photoelectric conversion by optical absorption between sub-bands in the quantum well layers
Implementation Method 3
Each of the first light receiving layer and the second light receiving layer includes, a first semiconductor layer that is doped with a first conductivity-type impurity, and a second semiconductor layer that is formed on the first semiconductor layer, and is doped with a second conductivity-type impurity which compensates the first conductivity-type impurity
Data Source
AI summary
An infrared detector includes, a substrate, a lower contact layer formed on the substrate, a first light receiving layer that is formed on the lower contact layer and has a quantum well structure, an intermediate contact layer formed on the first light receiving layer, a second light receiving layer that is formed on the intermediate contact layer and has a quantum well structure, and an upper contact layer formed on the second light receiving layer. Each of the first light receiving layer and the second light receiving layer includes, a first semiconductor layer that is doped with a first conductivity-type impurity, and a second semiconductor layer that is formed on the first semiconductor layer, and is doped with a second conductivity-type impurity which compensates the first conductivity-type impurity.