Ranging Device Waveguide Light Guidance Quantum Efficiency
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Solution Overview
Problem
Conventional ranging devices using the indirect time of flight method with silicon substrates face challenges in achieving sufficient quantum efficiency and resolution due to the trade-off between increasing substrate thickness for higher infrared transmittance and deteriorating signal-to-noise ratio, which complicates pixel separation and reduces resolution.
Innovation Solution
A ranging device is designed with a semiconductor layer, a photoelectric conversion section made of different materials, and a waveguide extending from the back surface to the front, where the waveguide has a higher refractive index than the semiconductor layer and is inclined, enhancing light guidance and quantum efficiency while maintaining thin semiconductor layers to prevent pixel crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the silicon substrate is increased to increase quantum efficiency, then quantum efficiency is improved, but separation between adjacent pixels becomes difficult and resolution deteriorates
Solution Approach 1:
The invention introduces a waveguide structure that segments and guides light from specific regions to specific photodiodes, preventing cross-talk between adjacent pixels. This segmentation approach allows the use of thinner substrates while maintaining both high quantum efficiency and resolution by directing light paths precisely to intended photodetectors without requiring thick substrates for light absorption.
Solution Approach 2:
The waveguide acts as an intermediary between the incident light and the photodiode array. It mediates the light transmission process by confining and directing light through total internal reflection, enabling efficient light guidance in thin substrates without requiring increased thickness for sufficient light absorption, thus resolving the contradiction between quantum efficiency and resolution.
2Illumination intensity
If the thickness of the silicon substrate is increased to improve infrared transmittance, then transmittance is improved, but signal-to-noise ratio deteriorates due to pixel crosstalk
Solution Approach 1:
The waveguide structure segments the light paths and confines them to specific regions, preventing cross-talk between adjacent photodiodes. This segmentation enables the use of thinner substrates that maintain high infrared transmittance while avoiding the pixel crosstalk that would otherwise occur and degrade the signal-to-noise ratio.
Solution Approach 2:
The invention changes the refractive index parameter by introducing a waveguide with higher refractive index than the surrounding silicon substrate. This parameter change enables total internal reflection and effective light confinement in thin substrates, achieving high transmittance without the need for increased thickness that would cause crosstalk and reduce signal-to-noise ratio.
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 improves quantum efficiency and resolution by effectively guiding light to the photoelectric conversion section without increasing semiconductor layer thickness, thereby enhancing sensitivity and maintaining high signal-to-noise ratio.
Implementation Method 1
a waveguide provided in the semiconductor layer so as to extend from the second surface to the photoelectric conversion section, the waveguide including a material different from the material of the semiconductor layer... The refractive index of the waveguide may be higher than the refractive index of the semiconductor layer
Implementation Method 2
a photoelectric conversion section that is in contact with the semiconductor layer on the side of the first surface, the photoelectric conversion section including a material different from a material of the semiconductor layer
Data Source
AI summary
To provide a ranging device having improved quantum efficiency and resolution. The present disclosure provides a ranging device including: a semiconductor layer having a first surface and a second surface opposite to the first surface; a lens on the second surface side; first and second charge storage sections in the semiconductor layer on the first surface side; a photoelectric conversion section that is in contact with the semiconductor layer on the first surface side, the photoelectric conversion section including a material different from a material of the semiconductor layer; first and second voltage application sections that apply a voltage to the semiconductor layer between the first and second charge storage sections and the photoelectric conversion section; and a waveguide provided in the semiconductor layer so as to extend from the second surface to the photoelectric conversion section, the waveguide including a material different from the material of the semiconductor layer.