Light Receiving Element With Graded Diffusion for Lower Dark Current
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Solution Overview
Problem
Semiconductor devices, such as avalanche photodiodes, face challenges with high dark current generation due to uniform zinc concentration distributions, leading to decreased sensitivity and noise.
Innovation Solution
A light receiving element with a semiconductor layer featuring a first impurity diffusion region and a second impurity diffusion region with a lower concentration, where the second region is formed around the first region through annealing, creating a gradual impurity concentration gradient that relaxes the electric field and concentrates it on a convex section, reducing dark current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform zinc concentration distribution is used in the semiconductor layer, then the manufacturing process is simple, but dark current increases and sensitivity decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform zinc concentration distribution where the impurity concentration varies in the depth direction. Specifically, the concentration is higher near the surface and gradually decreases toward the light-receiving interface, optimizing different regions for different functions: surface region for carrier collection and deeper region for light absorption with reduced dark current.
Solution Approach 2:
The patent changes the concentration parameter of zinc impurity throughout the semiconductor layer. By controlling the diffusion process to create a gradient distribution rather than uniform concentration, the device achieves improved performance. The concentration parameter varies continuously from the surface to the light-receiving interface, resolving the contradiction between manufacturing simplicity and device performance.
2Reliability
If a high impurity concentration is used in the diffusion region, then carrier collection efficiency improves, but dark current increases due to strong electric field
Solution Approach 1:
The patent applies local quality by creating different impurity concentration zones: a high-concentration region near the surface for efficient carrier collection and a lower-concentration region near the light-receiving interface to minimize dark current. This spatial variation in impurity concentration optimizes both carrier collection and dark current suppression in their respective regions.
Solution Approach 2:
Instead of using uniform high concentration throughout, the patent inverts the approach by using high concentration at the surface and gradually reducing it toward the light-receiving interface. This inverted concentration profile resolves the contradiction by placing high concentration where it benefits carrier collection and low concentration where it would generate harmful dark current.
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 solution effectively suppresses dark current generation, enhances sensitivity, and allows for smaller pixel sizes by optimizing the impurity diffusion regions in the semiconductor layer, improving the performance of semiconductor devices like avalanche photodiodes.
Implementation Method 1
a first impurity diffusion region provided on one surface of the semiconductor layer; and a second impurity diffusion region provided around the first impurity diffusion region
Implementation Method 2
forming a second impurity diffusion region around the first impurity diffusion region through annealing treatment
Data Source
AI summary
A light receiving element (1) according to an embodiment of the present disclosure includes: a semiconductor layer including a compound semiconductor material; a first impurity diffusion region (12A) provided on one surface of the semiconductor layer; and a second impurity diffusion region (12B) provided around the first impurity diffusion region (12A). The second impurity diffusion region (12B) has a lower impurity concentration than an impurity concentration of the first impurity diffusion region (12A).