Avalanche Photodiode Light Guide Structure for Higher Sensitivity
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Solution Overview
Problem
Existing photoelectric conversion elements, such as avalanche photodiodes, face challenges in efficiently guiding charges generated by photoelectric conversion to the avalanche multiplication region, which affects the light receiving sensitivity.
Innovation Solution
A photoelectric conversion element with a semiconductor layer structure that includes a light guide structure and an optical structure layer, where the light guide structure surrounds the avalanche multiplication region and is disposed over a depth of at least 0.8 μm from the second face, effectively guiding incident light to the avalanche multiplication region, enhancing light receiving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional light collecting structure is used, then the structure is simple, but the charge guiding efficiency to the avalanche multiplication region is insufficient
Solution Approach 1:
The light guide structure is divided into a first portion and a second portion with different configurations. The first portion has a first width and the second portion has a second width that is larger than the first width, creating a stepped structure that efficiently guides charges to the avalanche multiplication region while maintaining manageable complexity
Solution Approach 2:
The light guide structure extends in the depth direction with different portions at different depths. The second portion is disposed over a depth of at least 0.8 μm from the second face, utilizing the third dimension to improve charge guiding efficiency without proportionally increasing planar complexity
2Reliability
If the light guide structure is extended deeper, then the light receiving sensitivity improves, but the manufacturing precision requirement increases
Solution Approach 1:
The light guide structure has different widths at different portions: the first portion has a first width and the second portion has a second width that is larger than the first width. This local variation in geometry allows the structure to extend to sufficient depth (at least 0.8 μm) while maintaining manufacturing feasibility through gradual transitions
3Productivity
If the second portion width is increased, then the charge collection efficiency improves, but the device complexity increases
Solution Approach 1:
The light guide structure is segmented into a first portion and a second portion, where the second portion has a larger width than the first portion. This segmentation allows the structure to widen where needed for charge collection while maintaining a manageable overall complexity through modular design
Solution Approach 2:
The width of the light guide structure varies locally: the first portion has a first width and the second portion has a second width that is larger. This local quality variation optimizes charge collection efficiency at the second portion while keeping the first portion simpler
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 proposed solution efficiently guides charges to the avalanche multiplication region, thereby improving the light receiving sensitivity of the photoelectric conversion element, ensuring better photon detection efficiency and reducing shading effects.
Implementation Method 1
a light guide structure arranged in the semiconductor layer and having a first portion disposed so as to surround a first region in a plan view and a second portion disposed so as to surround a second region inside the first region in the plan view
Implementation Method 2
the second portion is disposed over a depth of at least 0.8 μm from the second face
Implementation Method 3
a second semiconductor region of a second conductivity type arranged closer to the second face than the first semiconductor region and forming a p-n junction with the first semiconductor region to form an avalanche photodiode
Implementation Method 4
an avalanche photodiode (hereinafter referred to as "APD") that multiplies charges generated by incidence of photons by avalanche breakdown
Data Source
AI summary
A photoelectric conversion element includes in a semiconductor layer a first semiconductor region arranged, a second semiconductor region arranged on a second face side closer than the first semiconductor region and forming a p-n junction with the first semiconductor region to form an avalanche photodiode, a light guide structure including a first portion surrounding a first region and a second portion surrounding a second region inside the first region in a plan view, and an optical structure layer disposed on the second face side. The second portion is disposed over a depth of at least 0.8 μm from the second face, the first and second semiconductor regions are arranged closer to the first face than the second portion, and the second portion overlaps at least a portion of an avalanche multiplication region between the first and second semiconductor region in the plan view.