Resonator Photodetector Structure Against Mirror Diffusion Damage
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Solution Overview
Problem
Resonator-type photoelectric conversion elements face challenges with sensitivity reduction due to metallic diffusion and damage from processing techniques, particularly when the distance between the resonator and the second reflecting mirror is short, leading to reduced crystallinity and photoelectric conversion efficiency.
Innovation Solution
The photoelectric conversion element is designed with a photoelectric conversion layer positioned on the substrate side relative to the resonator, and the resonator length is optimized to maintain sensitivity while minimizing the influence of the second reflecting mirror, using a distributed Bragg reflector and specific optical film thicknesses to enhance reflectance and reduce metal diffusion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the resonator and the second reflecting mirror is reduced, then the device size is minimized, but sensitivity is reduced due to metallic diffusion and processing damage
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the resonator and the second reflecting mirror. This dielectric layer acts as a protective barrier that prevents metallic diffusion from the second reflecting mirror to the photoelectric conversion layer, thereby maintaining high photoelectric conversion sensitivity even when the overall device size is minimized. The dielectric layer effectively mediates the interaction between the resonator and the second reflecting mirror, allowing close spacing without sacrificing performance.
2Object-generated harmful factors
If the photoelectric conversion layer is made thinner, then dark current is reduced, but sensitivity may be compromised
Solution Approach 1:
The patent utilizes resonance effects to change the optical parameters within the photoelectric conversion layer. By designing the resonator with specific optical path lengths that satisfy resonance conditions, light is confined and intensified within the thin photoelectric conversion layer, dramatically enhancing the interaction between light and the photoelectric conversion material. This resonance-enhanced light confinement allows the use of extremely thin photoelectric conversion layers (reducing dark current) while maintaining or even improving sensitivity through the resonant buildup of optical intensity.
3Use of energy by moving object
If metallic reflecting mirrors are used, then high reflectance is achieved, but metal diffusion causes damage to the photoelectric conversion layer
Solution Approach 1:
The patent employs a composite mirror structure consisting of alternating dielectric layers with different refractive indices (such as SiO2 and Si3N4) instead of pure metallic mirrors. This composite dielectric mirror achieves high reflectance through constructive interference of reflected light waves from multiple interfaces, matching or exceeding the reflectance of metallic mirrors. Crucially, this composite structure eliminates the metal diffusion problem entirely, as dielectric materials do not undergo thermal diffusion into the photoelectric conversion layer, thereby preserving the crystallinity and reliability of the photoelectric conversion layer.
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 configuration maintains high photoelectric conversion sensitivity while reducing the impact of metal diffusion and processing damage, achieving improved performance by securing the distance between the resonator and the photoelectric conversion layer and optimizing resonator length.
Implementation Method 1
The first reflecting mirror includes a distributed Bragg reflector (DBR) including a plurality of semiconductor layers
Implementation Method 2
In the above-described DBR, InP and InGaAsP are alternately layered to form a lower reflecting mirror
Implementation Method 3
light targeted for detection reciprocates through the photoelectric conversion layer a number of times due to the resonance effect
Implementation Method 4
resonator-type photoelectric conversion element with a photoelectric conversion layer sandwiched between two reflecting mirrors
Data Source
AI summary
A photoelectric conversion element includes a first reflecting mirror provided on a substrate, a resonator provided on the first reflecting mirror, and a second reflecting mirror provided on the resonator. The first reflecting mirror includes a distributed Bragg reflector (DBR) including a plurality of semiconductor layers. A photoelectric conversion layer is provided in at least one layer of the plurality of semiconductor layers.