Barrier Infrared Detector Structure for Lower Dark Current
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Solution Overview
Problem
Existing infrared detectors face challenges with generation-recombination dark current and surface leakage dark current, particularly in long-wavelength infrared (LWIR) detectors using type-II superlattice (T2SL) absorbers, which result in limited quantum efficiency and high dark current density.
Innovation Solution
The proposed solution involves an n+pBpnWn+ device structure, which includes a unipolar electron barrier positioned between a p-type absorber layer and a n-type absorber layer, along with a p-type recombination layer forming a p-n junction with an n-type top contact layer. This configuration reduces surface dark current by minimizing exposed absorber surfaces and provides adequate electrical isolation without the need to etch past the absorber p-n junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-n junction photodiode architecture is used in III-V semiconductor infrared absorbers, then the detector can achieve infrared detection functionality, but generation-recombination dark current increases due to Shockley-Read-Hall processes in the depletion layer
Solution Approach 1:
The patent extracts and removes the p-n junction depletion layer from the detector structure by using a unipolar n-type design without a p-type layer, thereby eliminating the source of generation-recombination dark current while maintaining infrared detection capability through the n-type absorber layer
Solution Approach 2:
Instead of using the conventional p-n junction architecture, the patent inverts the approach by implementing a unipolar n-type structure with a unipolar barrier, fundamentally changing the detection mechanism to avoid depletion layer-related dark current while preserving photodetection function
2Device complexity
If the surface conductivity type is entirely n-type in III-V semiconductor p-n junction infrared photodiodes, then the structure is simplified, but surface leakage dark current occurs
Solution Approach 1:
The patent applies local quality by creating a unipolar barrier region with specific electrical properties within the n-type structure, providing localized electrical isolation at critical interfaces to prevent surface leakage while maintaining overall structural simplicity and n-type dominance
3Reliability
If etching is performed past the absorber p-n junction to provide electrical isolation between pixels, then pixel isolation is improved, but the absorber surface is exposed increasing surface dark current
Solution Approach 1:
The patent eliminates the need for deep etching by removing the p-n junction structure entirely, using instead a unipolar n-type design where pixel isolation is achieved without exposing the absorber surface, thereby preventing surface dark current while maintaining electrical isolation
Solution Approach 2:
The patent performs preliminary structural design to avoid the need for post-fabrication etching isolation, incorporating electrical isolation functionality into the base unipolar structure itself, preventing the exposure problem before it can occur
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 n+pBpnWn+ device structure effectively reduces surface dark current and enhances quantum efficiency by minimizing exposed absorber surfaces and maintaining adequate electrical isolation, thus addressing the limitations of existing LWIR detectors.
Implementation Method 1
a unipolar electron barrier electrically connected to the p-type semiconductor layer; the unipolar electron barrier is positioned between the p-type semiconductor layer and the bottom absorber
Implementation Method 2
an infrared detector array including: a plurality of pixels, wherein each pixel including: an n-type semiconductor top contact layer; a p-type semiconductor layer electrically connected to the n-type top contact layer to form a top p-n junction
Implementation Method 3
a bottom absorber, wherein the unipolar electron barrier is positioned between the p-type semiconductor layer and the bottom absorber
Data Source
AI summary
Disclosed herein is an infrared detector. The detector includes a plurality of pixels. Each pixel includes an n-type semiconductor top contact layer, a p-type semiconductor layer electrically connected to the n-type top contact layer to form a top p-n junction, a unipolar electron barrier electrically connected to the p-type semiconductor layer, a bottom absorber, and an n-type semiconductor bottom contact layer electrically connected to the bottom absorber. The unipolar electron barrier is positioned between the p-type semiconductor layer and the bottom absorber.