iToF Ranging Sensor Structure for Quantum Efficiency and Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ranging devices using the indirect time of flight (iToF) method face challenges with insufficient quantum efficiency and reduced resolution due to the use of silicon substrates, which require increased thickness to improve efficiency but lead to signal-to-noise ratio deterioration and pixel separation issues.
Innovation Solution
A ranging device design incorporating a semiconductor layer with a photoelectric conversion section made of materials like germanium, InGaAs, or CIGS, and a metal layer with a protruding or recessed structure, along with charge storage sections and voltage application layers, enhances quantum efficiency and resolution by optimizing light reception and charge transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the silicon substrate is increased to improve quantum efficiency, then quantum efficiency is improved, but separation between adjacent pixels becomes difficult and resolution deteriorates
Solution Approach 1:
The invention divides the light receiving element into a semiconductor layer and a separate photoelectric conversion section, allowing independent optimization of each component. The semiconductor layer can be kept thin for good pixel separation while the photoelectric conversion section provides high quantum efficiency through materials like germanium or InGaAs.
Solution Approach 2:
The invention uses composite material structure by combining silicon-based semiconductor layer with germanium or InGaAs photoelectric conversion section. This composite approach allows the silicon layer to provide good electrical properties and pixel isolation, while the germanium/InGaAs layer provides high quantum efficiency for infrared detection.
2Reliability
If the thickness of the silicon substrate is increased to improve quantum efficiency, then quantum efficiency is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
By separating the light receiving element into thin semiconductor layer and distinct photoelectric conversion section, the invention reduces noise from charge carrier diffusion in thick substrates while maintaining high quantum efficiency in the optimized photoelectric conversion section.
Solution Approach 2:
The invention introduces a waveguide as an intermediary structure that guides incident light to the photoelectric conversion section, increasing light utilization efficiency and signal strength without requiring increased substrate thickness, thereby improving signal-to-noise ratio.
3Reliability
If a photoelectric conversion section made of different material is introduced, then quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The invention extracts the photoelectric conversion function from the bulk silicon substrate and places it in a dedicated photoelectric conversion section made of germanium or InGaAs. This extraction allows specialized material properties to be utilized while keeping the overall device structure manageable through clear functional separation.
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 design improves quantum efficiency and resolution by reducing dark current and increasing the amount of incident light on the photoelectric conversion section, while maintaining pixel separation and signal integrity.
Implementation Method 1
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 provided on the second surface side; first and second charge storage sections provided 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 first wire provided on the first surface side and electrically connected to the photoelectric conversion section.