Avalanche Photodiode Zn Diffusion Control
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Solution Overview
Problem
Conventional avalanche photodiodes face challenges in accurately controlling the thermal diffusion depth of Zn impurity, leading to reduced yield and productivity due to dispersion in wafer plane accuracy and fluctuation in device characteristics.
Innovation Solution
The use of a third group/fifth group semiconductor layer composed mainly of In and As for the semiconductor window layer allows for slower Zn diffusion, enabling precise control and higher reproducibility, thus improving manufacturing efficiency and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Zn is diffused thermally into InP to form the p-type conductive area, then the diffusion process is simple and straightforward, but the diffusion depth cannot be controlled accurately leading to dispersion in wafer plane accuracy
Solution Approach 1:
The patent changes the material parameter of the window layer from InP to a third group/fifth group semiconductor layer (such as AlInAs) composed mainly of In and As. This material substitution fundamentally alters the diffusion characteristics of Zn, enabling precise control of diffusion depth while maintaining manufacturing simplicity. The third group/fifth group semiconductor layer provides a more favorable diffusion environment for achieving reproducible device characteristics.
2Measurement precision
If the diffusion depth of Zn is controlled precisely to obtain desired device characteristics, then the frequency characteristic and electric characteristic improve, but it is difficult to achieve excellent reproducibility without dispersion in wafer plane
Solution Approach 1:
By changing the material composition parameter of the window layer to a third group/fifth group semiconductor layer, the patent achieves both precise diffusion depth control and excellent reproducibility across the wafer plane. The unique properties of this material composition create consistent diffusion behavior that eliminates the dispersion problems encountered with InP.
3Manufacturing precision
If Zn diffusion is performed in InP, then the process is conventional and well-established, but the diffusion velocity is high making it difficult to control diffusion depth accurately
Solution Approach 1:
The patent changes the material parameter of the window layer to a third group/fifth group semiconductor layer, which inherently provides a lower diffusion velocity for Zn compared to InP. This material substitution directly addresses the diffusion velocity issue while enabling accurate diffusion depth control.
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 results in an avalanche photodiode with enhanced reproducibility and yield, allowing for precise control of Zn diffusion depth and reduced electric field intensity, leading to improved reliability and productivity.
Implementation Method 1
Zn is diffused thermally in the third group/fifth group semiconductor layer composed of mainly In and As
Data Source
AI summary
The present invention provides an avalanche photodiode capable of raising productivity. An n-type InP buffer layer, an n-type GaInAs light absorption layer, an n-type GaInAsP transition layer, an n-type InP electric field adjusting layer, an n-type InP avalanche intensifying layer, an n-type AlInAs window layer and a p-type GaInAs contact layer are grown in order on an n-type InP substrate. Next, Be is ion-injected into an annular area along the outer periphery of a light receiving area which is activated by heat treatment so as to form an inclined joint, to obtain a p-type peripheral area for preventing an edge break down. Further, Zn is selectively diffused thermally into the light receiving area until it reaches the n-type InP avalanche intensifying layer so as to form a p-type conductive area.