Schottky-APD Pixel Structure for Long-Wavelength Light Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based avalanche photodiodes have a low absorption coefficient on the long wavelength side, resulting in poor sensitivity to the shortwave infrared (SWIR) range and similar wavelengths.
Innovation Solution
A photoelectric conversion device is designed with a semiconductor layer having avalanche photodiodes and Schottky barrier diodes, where the electrode pattern on the second principal surface includes recesses or a periodic concave-convex structure to enhance sensitivity, improving the interface area for photoelectric conversion and increasing absorption in the long wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional planar Schottky junction is used in silicon-based avalanche photodiodes, then the device structure is simple and easy to manufacture, but the absorption coefficient is low on the long wavelength side resulting in poor sensitivity to SWIR range
Solution Approach 1:
The patent transforms the planar Schottky junction into a three-dimensional structure by forming electrode patterns that extend into recesses of the semiconductor layer. This dimensional change increases the effective interface area between the electrode and semiconductor, thereby enhancing light absorption in the long wavelength range without significantly complicating the manufacturing process
Solution Approach 2:
The patent creates a structure with controlled voids by forming recesses in the semiconductor layer and filling them with electrode material. This porous-like structure increases the surface area available for photoelectric conversion, improving absorption coefficient for long wavelengths while maintaining structural integrity
2Reliability
If the interface area of Schottky junction is increased by adding structures like recesses or concave-convex patterns, then light absorption is enhanced and sensitivity to long wavelength improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent divides the semiconductor layer into regions with different depths by forming an array of recesses. This segmentation allows light to interact with multiple interfaces at different depths, enhancing absorption probability for long wavelength photons while using standard semiconductor fabrication techniques
Solution Approach 2:
By extending the electrode-patterned Schottky junction into the third dimension (depth) through recess formation, the patent increases the effective absorption path length and interface area without requiring lateral expansion of the device, thus improving absorption while maintaining compact form factor
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 device demonstrates improved sensitivity to long wavelength ranges by increasing the interface area of the Schottky junction and enhancing light absorption, overcoming the limitations of silicon-based photodiodes in the SWIR range.
Implementation Method 1
a photoelectric conversion element using an avalanche photodiode (APD) that causes avalanche multiplication capable of detecting faint light of a single photon level
Implementation Method 2
an avalanche photodiode arranged in the semiconductor layer
Implementation Method 3
a Schottky barrier diode constituted by the semiconductor layer and an electrode pattern in contact with the second principal surface
Implementation Method 4
the second principal surface has a periodic concave-convex structure
Data Source
AI summary
A photoelectric conversion device in which a plurality of pixels are arranged in a semiconductor layer having a first principal surface and a second principal surface is provided. Each of the plurality of pixels includes: an avalanche photodiode arranged in the semiconductor layer; and a Schottky barrier diode constituted by the semiconductor layer and an electrode pattern in contact with the second principal surface. In an orthogonal projection to the second principal surface, the second principal surface has a region overlapping the avalanche photodiode, and the region includes a first region in contact with the electrode pattern and a second region in contact with an insulating layer.