Germanium-Silicon Photodiode for Near-Infrared Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional silicon-based image sensors have low optical absorption efficiency for near-infrared (NIR) wavelengths, limiting their performance in various applications.
Innovation Solution
The use of germanium or germanium-silicon materials in photodiodes, integrated with silicon on a common substrate, to enhance the operating wavelength range, sensitivity, and speed of optical sensors, allowing for efficient detection of both visible and NIR light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon-based photodiodes are used for optical detection, then the device structure is simple and manufacturing is easy, but the optical absorption efficiency for near-infrared wavelengths is low
Solution Approach 1:
The patent employs a composite material structure consisting of a silicon substrate with a germanium layer deposited on its surface. The silicon substrate provides mechanical support and ease of manufacture, while the germanium layer provides high optical absorption efficiency for near-infrared wavelengths. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both manufacturability and high optical absorption.
2Reliability
If germanium or germanium-silicon photodiodes are used to increase sensitivity and extend wavelength range, then the optical absorption efficiency and operating wavelength range improve, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The photodiode is segmented into distinct functional layers: a silicon substrate providing structural support and a separate germanium layer providing enhanced optical absorption. This segmentation allows each layer to be optimized for its specific function while simplifying the overall manufacturing process compared to creating a completely new complex device structure.
Solution Approach 2:
By using a composite structure of silicon and germanium layers, the patent achieves high optical absorption efficiency for near-infrared wavelengths without requiring complete redesign of the entire device. The composite material approach allows leveraging the advantageous properties of both materials while maintaining relatively simple device architecture.
3Ease of manufacture
If a single material is used for photodiode fabrication, then the manufacturing process is simple, but the operating wavelength range is limited
Solution Approach 1:
The patent uses a composite material system with silicon substrate and germanium layer, where each material contributes to different wavelength ranges. Silicon handles visible and shorter wavelength detection, while germanium extends the response to near-infrared wavelengths. This composite approach enables multi-wavelength operation while maintaining compatibility with standard silicon manufacturing processes.
Solution Approach 2:
The photodiode structure is designed to perform multiple functions: detecting both visible and near-infrared wavelengths using the same basic device architecture. The silicon-germanium composite structure provides universal detection capability across a broad spectral range, eliminating the need for separate devices for different wavelength ranges.
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 approach increases the dynamic range and bandwidth of optical sensors, enabling higher modulation frequencies, improved depth resolution, and reduced crosstalk, while also reducing manufacturing costs and packaging complexity.
Implementation Method 1
germanium, germanium-silicon, or germanium-tin may be used as image sensor materials with innovative optical device structure design described in this specification
Implementation Method 2
Conventionally, silicon is used as an image sensor material
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An optical sensor including a semiconductor substrate; a first light absorption region formed in the semiconductor substrate, the first light absorption region configured to absorb photons at a first wavelength range and to generate photo-carriers from the absorbed photons; a second light absorption region formed on the first light absorption region, the second light absorption region configured to absorb photons at a second wavelength range and to generate photo-carriers from the absorbed photons; and a sensor control signal coupled to the second light absorption region, the sensor control signal configured to provide at least a first control level and a second control level.