High-Index Substrate Photodetector Wavelength Extension
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Solution Overview
Problem
Conventional photodetectors with superlattice structures face challenges in extending their operational wavelength without reducing the absorption coefficient, as increasing the superlattice period can lead to reduced absorption efficiency.
Innovation Solution
Modifying the substrate crystal orientation to high-Miller index orientations, such as (211) or (311), allows for a red-shift in photoluminescence and cut-off wavelengths without altering the superlattice period or composition, enhancing quantum efficiency and enabling long-wave infrared detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the superlattice period is increased to extend the operational wavelength, then the photodetector responds to longer wavelengths, but the absorption coefficient per unit thickness is reduced
Solution Approach 1:
The patent changes the substrate crystal orientation parameter from conventional (100) to high-index orientations such as (211) or (311). This parameter change in the substrate orientation induces piezoelectric effects and modifies the band structure, enabling the superlattice to achieve red-shifted photoluminescence and extended long-wave infrared response without increasing the superlattice period, thereby maintaining high absorption coefficient while extending operational wavelength
2Length of stationary object
If the superlattice period is increased to achieve red-shifted response, then the cut-off wavelength is extended, but the quantum efficiency is reduced due to reduced absorption per unit thickness
Solution Approach 1:
The patent modifies the substrate orientation parameter to high-index orientations, which generates piezoelectric fields that enhance carrier separation and collection efficiency. This parameter change enables extended cut-off wavelength into the long-wave infrared range while maintaining high quantum efficiency through improved charge carrier dynamics rather than relying on increased superlattice period
Solution Approach 2:
The patent replaces the mechanical approach of increasing superlattice period with a field-based approach utilizing piezoelectric effects generated by high-index substrate orientation. The piezoelectric field substitutively provides the necessary band structure modification and carrier separation mechanism, achieving extended wavelength response with maintained quantum efficiency
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 enables high-performance long-wave infrared photodetectors with extended wavelength response ranges, leveraging piezo-electric effects and alloy ordering to achieve higher quantum efficiency without increasing the superlattice period, thus maintaining absorption efficiency.
Implementation Method 1
leveraging piezo-electric effects and alloy ordering to achieve higher quantum efficiency without increasing the superlattice period
Implementation Method 2
leveraging piezo-electric effects and alloy ordering to achieve higher quantum efficiency without increasing the superlattice period
Implementation Method 3
Photodetectors generally provide an electronic signal indicative of incident light
Data Source
AI summary
A layered structure used for detecting incident light includes a substrate having a surface with a high Miller index crystal orientation and a superlattice structure formed over the substrate at the surface. The superlattice structure is aligned to the high Miller index crystal orientation and exhibits a red-shifted long wave infrared response range based on the crystal orientation as compared to a superlattice structure formed over a substrate at a surface with a (100) crystal orientation.