Bragg Reflector Light Absorption Structure for Thin Near-IR Sensing
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Solution Overview
Problem
Conventional semiconductor materials for light sensing devices, such as silicon, exhibit low absorbance for long-wavelength light, necessitating increased thickness or additional materials, which are difficult to implement and not compatible with standard processing operations.
Innovation Solution
A resonator-based light absorption structure featuring a semiconductor layer with a distributed Bragg reflector layer having holes with gradually changing widths, and a reflective layer, designed to enhance light absorbance by achieving critical coupling and nearly perfect absorption in the near-infrared wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the semiconductor device is increased to compensate for low absorbance, then light absorbance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the structural parameters of the semiconductor device by introducing a distributed Bragg reflector with periodically varying refractive index and a resonant cavity structure. These parameter changes enable the thin device to achieve high light absorbance through resonant enhancement, avoiding the need for increased thickness while maintaining or improving absorption performance.
Solution Approach 2:
The patent employs a composite structure combining the distributed Bragg reflector (made of alternating high and low refractive index layers) with the resonant cavity and absorptive medium. This composite design creates synergistic effects where the DBR provides selective reflection and the cavity provides resonant enhancement, achieving high absorbance in a thin configuration that would be impossible with a single homogeneous material.
2Reliability
If additional materials are added to improve light absorbance, then absorbance performance is improved, but compatibility with standard semiconductor processing is worsened
Solution Approach 1:
The patent achieves improved absorbance by changing the structural parameters (refractive index distribution, layer thicknesses, periodicity) of the semiconductor device itself rather than introducing exotic materials. The distributed Bragg reflector uses standard semiconductor materials with different refractive indices arranged in a periodic structure, and the resonant cavity uses conventional semiconductor layers, all of which are compatible with standard semiconductor fabrication processes.
Solution Approach 2:
The patent maintains homogeneity by using materials that are consistent with standard semiconductor processing throughout the device structure. The distributed Bragg reflector consists of alternating layers of common semiconductor materials (such as SiO2 and Si3N4 or different doped regions of silicon), and the resonant cavity uses the same semiconductor substrate material, ensuring uniform processing conditions and compatibility with existing manufacturing infrastructure.
3Ease of manufacture
If a thin structure is used to maintain manufacturing simplicity, then ease of manufacture is improved, but light absorbance deteriorates
Solution Approach 1:
The patent applies the principle of optical resonance (analogous to mechanical vibration) by designing a resonant cavity that supports specific optical modes. When incident light matches the resonant frequency of the cavity, the light field is strongly enhanced within the thin absorptive region, dramatically increasing the absorption efficiency. This resonant enhancement mechanism allows thin structures to achieve high absorbance that would otherwise require much thicker materials.
Solution Approach 2:
The patent uses parameter changes in the form of a distributed Bragg reflector with specifically designed layer thicknesses and refractive index contrasts to create strong optical confinement and resonance. By precisely controlling these parameters (layer thickness, refractive index difference, number of periods), the device achieves high absorbance in a thin configuration, overcoming the typical limitation that thin structures have low absorption.
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 solution achieves high absorbance of long-wavelength light, including near-infrared wavelengths, with a thin structure, enabling efficient light sensing while maintaining compatibility with existing semiconductor processing techniques.
Implementation Method 1
A resonator-based light absorption structure may include a first semiconductor layer configured to be an optical cavity of the resonator; a distributed Bragg reflector layer including a plurality of holes on a first surface of the first semiconductor layer
Implementation Method 2
designed to enhance light absorbance by achieving critical coupling and nearly perfect absorption in the near-infrared wavelength band
Implementation Method 3
a reflective layer on a second surface of the first semiconductor layer, the second surface of the first semiconductor layer opposite to the first surface of the first semiconductor layer
Data Source
AI summary
A light sensing device includes a semiconductor layer including a distributed Bragg reflector including a first surface of the semiconductor layer, and a photoelectric conversion unit including a second surface of the semiconductor layer, and the distributed Bragg reflector has a plurality of holes each having, in a cross-sectional view, a width gradually changing from a first width to a second width according to a width change period; a first electrode in one region of the semiconductor layer; and a second electrode on the second surface of the semiconductor layer and having a reflective metal.