Wide Bandgap Layer for Imaging Detector Quantum Efficiency
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Solution Overview
Problem
Existing imaging detectors with narrow bandgap dielectric/passivation layers suffer from reduced quantum efficiency due to negative charging and trapping of photo-generated holes, especially at cryogenic temperatures, when exposed to short-wavelength UV or visible radiation.
Innovation Solution
A substrate-removed imaging detector assembly with a wide bandgap layer, such as Y2O3, MgF2, or CaF2, is integrated with the anti-reflective coating layer, preventing electron injection and maintaining a flat energy band diagram, thus preventing the formation of an inversion region and enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow bandgap dielectric/passivation layer is used in the anti-reflective coating, then the refractive index matching is improved, but electron injection into the layer occurs causing negative charging and hole trapping that reduces quantum efficiency
Solution Approach 1:
The patent changes the bandgap parameter of the dielectric layer from narrow to wide bandgap material. This parameter change prevents electron injection into the dielectric layer while maintaining the refractive index matching function, thereby eliminating negative charging and hole trapping that reduce quantum efficiency.
Solution Approach 2:
The patent uses a composite structure combining wide bandgap dielectric material with specific refractive index properties. This composite material approach allows simultaneous achievement of refractive index matching for anti-reflection and high bandgap for electron blocking, resolving the contradiction between optical performance and electrical stability.
2Reliability
If the anti-reflective coating is applied to match refractive index of HgCdTe to air/vacuum, then quantum efficiency is improved, but the back interface becomes susceptible to electron injection and inversion layer formation
Solution Approach 1:
The patent modifies the energy band parameter of the dielectric layer by selecting wide bandgap material. This change creates a higher conduction band edge that prevents electron injection from the HgCdTe back interface, eliminating the formation of inversion layers while preserving the refractive index matching function.
3Productivity
If continuous exposure to short-wavelength UV or visible radiation occurs, then photo charge generation is enhanced, but negative charging accumulates progressively reducing detector performance
Solution Approach 1:
The patent converts the harmful effect of short-wavelength radiation (which generates energetic electrons capable of injection) into a beneficial outcome by using wide bandgap material that is immune to such injection. The high-energy photons still generate photo charge effectively, but the dielectric layer prevents the harmful cumulative charging effect.
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 integration of a wide bandgap layer prevents electron charging and hole trapping, maintaining high collection efficiency even under continuous exposure to short-wavelength radiation, improving quantum efficiency and detector performance across near-UV, visible, and infrared wavelengths.
Implementation Method 1
The wide band-gap layer has a conduction band at a first energy level greater than a second energy level of photo-generated hot electrons, for preventing formation of an inversion region proximal to an interface portion between the anti-reflective coating layer and the imaging detector assembly
Implementation Method 2
A wide bandgap layer is deposited on the imaging detector assembly in a vacuum chamber using for example electron beam evaporation
Implementation Method 3
A wide bandgap layer is deposited on the imaging detector assembly in a vacuum chamber using for example electron beam evaporation
Data Source
AI summary
A substrate-removed, surface passivated, and anti-reflective (AR) coated detector assembly is provided. The assembly has an AR coating or passivation layer which includes a wide bandgap thin-film dielectric/passivation layer integrated therein. The wide bandgap thin-film dielectric/passivation layer is positioned proximal to a back interface of a substrate-removed detector assembly. A method of manufacturing the detector assembly includes etching a backside of a partially-removed-substrate detector assembly to obtain an etched detector assembly removed from a substrate. A wide bandgap layer is deposited, in a vacuum chamber, on the etched detector assembly without utilizing an adhesive layer. Additional anti-reflective coating layers are deposited, in the same vacuum chamber, on the wide bandgap layer to form an anti-reflective coating layer with the wide bandgap layer integrated therein. The wide bandgap layer is positioned proximal to an interface portion between the anti-reflective coating layer and the detector assembly.