P-i-n Photodetector Doping Profile for Higher Infrared Quantum Efficiency
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Solution Overview
Problem
Infrared photodetectors using semiconductor nanocrystals or thin-film materials face limitations in quantum efficiency due to the restricted thickness of depletion regions at the absorber/channel interface, which impairs their ability to effectively absorb infrared radiation.
Innovation Solution
A p-i-n type doping profile is implemented in the semiconductor nanocrystal absorber and adjacent channel, significantly increasing the depletion region thickness and enhancing quantum efficiency for infrared wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If semiconductor nanocrystals or thin-film materials are used as absorbers in infrared photodetectors, then the spectral response can be extended to infrared wavelengths, but the depletion region thickness is limited to about 100 nm which reduces quantum efficiency
Solution Approach 1:
The patent changes the doping parameters of the absorber material by creating a graded doping profile where the doping concentration varies through the thickness of the absorber layer. This allows extension of the depletion region into the bulk of the absorber material while maintaining the infrared spectral response, thereby increasing quantum efficiency without limiting the spectral range
Solution Approach 2:
The patent employs a composite structure combining semiconductor nanocrystals embedded in a matrix material or thin-film layers with specific doping profiles. This composite approach enables both infrared absorption capability and extended depletion region thickness, resolving the contradiction between spectral response and quantum efficiency
2Reliability
If high doping concentrations are used in the absorber material, then the electrical conductivity is improved, but the depletion region thickness decreases which limits light absorption
Solution Approach 1:
The patent applies local quality by implementing a graded doping profile where different regions of the absorber layer have different doping concentrations. The region closer to the junction has higher doping for good electrical contact, while deeper regions have lower doping to extend the depletion region, thus achieving both good conductivity and thick depletion region
Solution Approach 2:
The patent changes the doping concentration parameter as a function of position through the absorber layer thickness. This spatial variation of the doping parameter allows the depletion region to extend deeper into the material while maintaining sufficient electrical conductivity at the junction interface
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 allows for improved absorption and conversion of infrared radiation, significantly increasing the quantum efficiency of photodetectors by extending the built-in electric field and enhancing the capture of infrared light.
Implementation Method 1
When electromagnetic radiation is absorbed in the photoactive layer, the photogenerated charges can be separated so that one charge-carrier type is trapped in the photoactive layer while another carrier type is transferred to the measurement layer
Implementation Method 2
the photogenerated charges can be separated so that one charge-carrier type is trapped in the photoactive layer while another carrier type is transferred to the measurement layer
Data Source
AI summary
A photodetector which comprises a measurement layer (15) and at least a first photoactive layer (11) which covers the measurement layer (15). The measurement layer (15) may be a transistor channel or a charge accumulation electrode. The conductivity type of the measurement layer is n-type, p-type or ambipolar and the first photoactive layer (11) exhibits intrinsic semiconductivity.