Resonant-Cavity Infrared Photodetectors with Fully-Depleted Absorbers
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Solution Overview
Problem
Conventional infrared (IR) detectors struggle to achieve high detectivity in the shortwave, midwave, and longwave infrared regions using resonant cavity enhancement, as previous attempts have performed below state-of-the-art levels for conventional broadband IR detectors, particularly due to materials-related issues with lead-salt detectors and the need for thick absorber regions in HgCdTe and III-V designs.
Innovation Solution
The development of resonant-cavity infrared photodetectors with a thin absorber layer fully depleted within the resonant cavity, utilizing a type-II InAs-GaSb interface or quantum well structures, and ion-bombarded p-regions to suppress dark currents, allowing for high quantum efficiency and reduced dark current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thick absorber region is used in conventional broadband IR detectors to achieve high quantum efficiency, then quantum efficiency is improved, but dark current density increases
Solution Approach 1:
The absorber region is segmented into multiple quantum wells separated by barrier layers, creating a superlattice structure. This segmentation allows the total absorber thickness to be divided into thinner active regions with lower dark current generation, while maintaining overall high quantum efficiency through the cumulative effect of multiple quantum wells.
Solution Approach 2:
Different regions of the absorber are given different properties: the quantum well regions are optimized for high absorption coefficient and carrier generation, while the barrier regions are optimized for carrier blocking and dark current suppression. This local differentiation allows simultaneous optimization of quantum efficiency and dark current reduction.
2Object-generated harmful factors
If resonant cavity enhancement is used to reduce absorber thickness, then dark current density is reduced, but detectivity performance remains below state-of-the-art levels
Solution Approach 1:
The detector employs a composite structure combining resonant cavity optics with III-V semiconductor quantum well superlattice absorbers. This composite approach integrates the dark current reduction benefits of thin-cavity designs with the high detectivity performance of engineered quantum well materials, achieving detectivity at or above state-of-the-art levels while maintaining reduced dark current.
3Object-generated harmful factors
If the absorber thickness is reduced to achieve full depletion, then dark current is minimized, but quantum efficiency decreases without resonant cavity enhancement
Solution Approach 1:
The resonant cavity structure creates optical resonance conditions that cause light to oscillate multiple times through the thin absorber region. This resonant enhancement effectively increases the interaction length between light and absorber material, compensating for the reduced physical thickness and maintaining high quantum efficiency despite the thin absorber design.
Solution Approach 2:
The resonant cavity enables continuous optical circulation within the thin absorber region, allowing photons to pass through the absorber multiple times in sequence. This continuous action ensures that sufficient photons are absorbed to generate high quantum efficiency, even though the physical path length through the absorber is short.
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 approach significantly enhances detectivity by minimizing dark current and maintaining high quantum efficiency, enabling background-limited sensitivity at higher temperatures without cryogenic cooling, suitable for applications like chemical sensing.
Implementation Method 1
RCIDs typically form a resonant cavity along the vertical axis by positioning two mirrors above and below the absorber. Thanks to the mirrors, any incident light with a wavelength tuned to the resonant mode of the cavity makes multiple passes through the absorber.
Implementation Method 2
QE is the device external quantum efficiency, representing the fraction of incident photons that produce an electron-hole pair that is collected to produce electrical current
Implementation Method 3
ion-bombarded p-regions to suppress dark currents
Data Source
AI summary
Resonant-cavity infrared photodetector (RCID) devices that include a thin absorber layer contained entirely within the resonant cavity. In some embodiments, the absorber is a single type-II InAs—GaSb interface situated between an AlSb/InAs superlattice n-type region and a p-type AlSb/GaSb region. In other embodiments, the absorber region comprises quantum wells formed on an upper surface of the n-type region. In other embodiments, the absorber region comprises a “W”-structured quantum well situated between two barrier layers, the “W”-structured quantum well comprising a hole quantum well sandwiched between two electron quantum wells. In other embodiments, the RCID includes a thin absorber region and an nBn or pBp active core within a resonant cavity. In some embodiments, the RCID is configured to absorb incident light propagating in the direction of the epitaxial growth of the RCID structure, while in other embodiments, it absorbs light propagating in the epitaxial plane of the structure.