Infrared Light-Receiving Device With Impurity Gradient Optical Filter
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Solution Overview
Problem
Infrared light-receiving devices with InGaAs/GaAsSb type-II quantum wells exhibit sensitivity variations with wavelength, limiting their application range due to differences in sensitivity across different wavelengths.
Innovation Solution
An infrared light-receiving device is designed with a substrate, an optical absorption layer featuring a type-II superlattice structure, and an optical filter comprising semiconductor regions with varying n-type InGaAs layers, where the impurity concentration gradients in the filter adjust the optical band gap energies to compensate for wavelength-dependent sensitivity, allowing for improved uniformity in optical response characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an InGaAs/GaAsSb type-II superlattice structure is used for optical absorption, then sensitivity in the near-infrared wavelength region (1.3 to 2.5 micrometers) is achieved, but wavelength-dependent sensitivity variations occur that narrow the application range
Solution Approach 1:
The patent applies parameter changes by varying the n-type impurity concentration across different semiconductor regions in the optical filter. Specifically, the first semiconductor region has an impurity concentration of 2.0×10^19 cm^-3 or more, the third semiconductor region has 3.0×10^18 cm^-3 or less and 8.0×10^17 cm^-3 or more, and the second semiconductor region has an intermediate concentration. This gradient in impurity concentration modifies the optical band gap energies to compensate for wavelength-dependent sensitivity variations, thereby improving sensitivity uniformity while maintaining broad application range.
2Reliability
If a single-layer optical filter is used, then device complexity is reduced, but the ability to compensate for wavelength-dependent sensitivity is insufficient
Solution Approach 1:
The optical filter is segmented into three distinct semiconductor regions with different n-type impurity concentrations. This segmentation allows each region to contribute differently to the optical filtering, with the first region (highest impurity concentration) addressing shorter wavelengths, the third region (lowest impurity concentration) addressing longer wavelengths, and the second region (intermediate concentration) providing transitional compensation. This multi-region structure enables effective compensation for wavelength-dependent sensitivity across the entire 1.3 to 2.5 micrometer range.
Solution Approach 2:
Each semiconductor region within the optical filter is assigned a specific local quality through controlled n-type impurity concentration. The first semiconductor region has high impurity concentration (2.0×10^19 cm^-3 or more) optimized for certain wavelength ranges, while the third semiconductor region has low impurity concentration (3.0×10^18 cm^-3 or less) optimized for other wavelength ranges. This local differentiation of material properties enables precise compensation for wavelength-dependent sensitivity variations without requiring a completely complex multi-component system.
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 device achieves enhanced optical response characteristics across a broader wavelength range, expanding the applicability of infrared light-receiving devices by compensating for sensitivity variations, thereby improving their performance and versatility.
Implementation Method 1
InGaAs with an n-type impurity concentration of more than 8.0×10^17 cm−3 exhibits an optical band gap energy that is larger than the band gap energy of InGaAs because of the Moss-Burstein effect. Consequently, light having an energy larger than the band gap energy of InGaAs and smaller than the optical band gap energy is absorbed by InGaAs doped with an n-type impurity having a low concentration of 8.0×10^17 cm−3 or less and undoped InGaAs, but passes through InGaAs doped with an n-type impurity having a relatively high concentration of more than 8.0×10^17 cm−3
Data Source
AI summary
An infrared light-receiving device includes an optical absorption layer disposed on a principal surface of a substrate and an optical filter disposed on the optical absorption layer, the optical filter including first, second, and third semiconductor regions that are arranged in that order in a direction from the optical absorption layer to the optical filter, each of the first, second, and third semiconductor regions including an n-type InGaAs layer. The optical absorption layer includes a type-II superlattice structure. The first semiconductor region contains an n-type impurity with a concentration of 2.0×1019 cm−3 or more. The third semiconductor region contains an n-type impurity with a concentration of 3.0×1018 cm−3 or less and 8.0×1017 cm−3 or more. The second semiconductor region contains an n-type impurity with a concentration between the impurity concentration of the first semiconductor region and the impurity concentration of the third semiconductor region.