Time of Flight Sensor with Epitaxial Ge-Si Photosensitive Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time of flight sensors using Si as detector material at 900 nm wavelength exhibit poor light absorption, leading to reduced accuracy due to the need for thick Si absorbing structures, while Ge offers better absorption but with higher measurement uncertainty.
Innovation Solution
A time of flight sensor design featuring an epitaxially-grown Ge-based photosensitive structure with a Si-based photocurrent collecting structure, separated by a dielectric material layer, and configured with n- and p-contacts within the photocurrent collecting structure to reduce measurement uncertainty by effectively collecting both electron and hole currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Si is used as detector material at 900 nm wavelength, then the sensor structure is simple and Si properties are well-mastered, but light absorption is poor requiring thick absorbing structures which reduces accuracy
Solution Approach 1:
The patent combines Si and Ge materials in a single sensor structure, with Ge used for light absorption at 900 nm wavelength and Si providing the substrate and electrical properties. This composite approach allows thin absorbing structures to achieve high light absorption efficiency, resolving the contradiction between accuracy and structure thickness.
2Measurement precision
If Ge is used as detector material, then light absorption coefficient is higher enabling operation at larger wavelengths, but measurement uncertainty increases
Solution Approach 1:
By combining Ge photosensitive layer with Si substrate and electrical structures, the patent achieves high light absorption from Ge while maintaining reliable electrical properties and low measurement uncertainty through Si's well-mastered characteristics.
Solution Approach 2:
The patent applies different materials to different functional regions: Ge is used specifically in the photosensitive area where light absorption is critical, while Si is used in the substrate and electrical structures where electrical stability is critical. This local optimization resolves the contradiction between absorption efficiency and measurement reliability.
3Ease of manufacture
If thick Si absorbing structures are used to compensate for poor light absorption, then the sensor can be fabricated with Si, but the measurement accuracy is reduced
Solution Approach 1:
The patent uses a composite Si-Ge structure where a thin Ge layer provides high light absorption efficiency, eliminating the need for thick Si structures. This maintains fabrication simplicity through epitaxial growth while achieving high measurement accuracy through Ge's superior optical properties.
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 design enhances the accuracy and efficiency of time of flight sensors by improving light absorption and reducing material consumption and ohmic losses, contributing to energy and resource savings, and aligning with green technology solutions.
Implementation Method 1
Time of flight sensors may use infrared light which is invisible to the human eye... Ge as detector material has a higher absorption coefficient in the 900 nm range and it can also absorb photons at larger wavelength than Si
Implementation Method 2
an epitaxially-grown Ge-based photosensitive structure including an upper portion and a trunk portion
Data Source
AI summary
A time of flight sensor includes at least one pixel, including: an epitaxially-grown Ge-based photosensitive structure including an upper portion and a trunk portion, a Si-based photocurrent collecting structure, a dielectric material layer arranged at least between the upper portion of the photosensitive structure and the photocurrent collecting structure, wherein the trunk portion of the photosensitive structure is arranged within an aperture in the dielectric material layer, and at least one n-contact configured to collect electrons of a photocurrent and at least one p-contact configured to collect holes of the photocurrent, the at least one n-contact and p-contact arranged in the photocurrent collecting structure.