Backside Incident Photodiode Array Carrier Capturing
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Solution Overview
Problem
Backside incident type photodiode arrays experience high crosstalk due to carrier diffusion beyond depletion layers, leading to signal interference and reduced photosensitivity, especially when a photodiode falls into an electrically floating state.
Innovation Solution
Incorporating a carrier capturing portion with pn-junctions between adjacent photodiodes on the semiconductor substrate, which captures and redirects diffusing carriers, thereby reducing crosstalk and maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a backside incident type photodiode array is used, then the photosensitivity is improved, but crosstalk occurs between adjacent photodiodes due to carrier diffusion
Solution Approach 1:
An n-type carrier capturing region is introduced as an intermediary structure between adjacent photodiodes. This region acts as a mediator that captures and removes carriers through diffusion before they can reach adjacent photodiodes, thereby eliminating crosstalk while preserving the backside incident configuration's photosensitivity advantages
2Object-generated harmful factors
If carrier capturing regions are formed between all adjacent photodiodes, then crosstalk is suppressed, but the device complexity increases
Solution Approach 1:
The carrier capturing regions are segmented and selectively positioned only at corners and edges of the photodiode array where crosstalk is most problematic, rather than forming continuous barriers between all adjacent photodiodes. This segmentation reduces the total amount of additional structure while maintaining effective crosstalk suppression at critical locations
Solution Approach 2:
Carrier capturing regions are locally introduced only at specific positions (corners and edges) where geometric factors cause enhanced carrier diffusion and crosstalk, rather than uniformly across the entire array. This local quality approach addresses problem areas without unnecessarily complicating regions where crosstalk is already minimal
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
Effectively suppresses crosstalk between photodiodes while maintaining or enhancing photosensitivity, even when a photodiode becomes electrically floating, resulting in improved resolution and signal stability.
Implementation Method 1
carriers generated in regions other than a depletion layer in the semiconductor substrate migrate by diffusion over a long distance
Implementation Method 2
a carrier capturing portion having one or a plurality of carrier capturing regions, respectively including pn-junctions
Data Source
AI summary
A photodiode array PD1 comprises an n-type semiconductor substrate one face of which is an incident surface of light to be detected; a plurality of pn junction-type photosensitive regions 3 as photodiodes formed on the side of a detecting surface that is opposite to the incident surface of the semiconductor substrate; and a carrier capturing portion 12 formed between adjacent photosensitive regions 3 from among the plurality of photosensitive regions 3 on the detecting surface side of the semiconductor substrate. The carrier capturing portion 12 has one or plurality of carrier capturing regions 13 respectively including pn-junctions, arranged at intervals. Thereby can be realized a semiconductor photodetector and a radiation detecting apparatus which can favorably restrain crosstalk from occurring.