Mg2Si Photodiode Electrode Structure for Adhesion and Carrier Collection
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Solution Overview
Problem
Photodiodes using magnesium silicide (Mg2Si) face challenges with electrode adhesion and energy barriers at the semiconductor/electrode interface, affecting photosensitivity and durability, particularly due to the poor work function mismatch between Mg2Si and conventional electrode materials like Ti.
Innovation Solution
Selecting electrode materials with work functions matching or exceeding 4.81 eV for p-type Mg2Si and less than 4.81 eV for n-type Mg2Si, allowing for the formation of silicides or alloys with Mg2Si, such as nickel, cobalt, and aluminum, to eliminate energy barriers and enhance adhesion and photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gold (Au) electrode is used for Mg2Si photodiode, then conductivity and chemical stability are improved, but adhesion at the contact interface deteriorates
Solution Approach 1:
The patent introduces a Ti adhesion layer as an intermediary between the Au electrode and the Mg2Si semiconductor. This Ti layer serves as a mediator that provides both good adhesion to the semiconductor and compatibility with the Au electrode, resolving the adhesion problem while maintaining the chemical stability and conductivity benefits of the Au electrode.
Solution Approach 2:
The electrode structure is designed as a composite material system consisting of multiple layers (Ti adhesion layer + Au electrode layer). This composite structure combines the advantages of different materials: Ti provides adhesion to the semiconductor, while Au provides conductivity and chemical stability, achieving overall performance improvement.
2Strength
If Ti is interposed between Au electrode and Mg2Si contact surface, then adhesion is improved, but photosensitivity deteriorates due to energy barrier
Solution Approach 1:
The patent optimizes the thickness parameter of the Ti adhesion layer to a specific range (1 nm to 10 nm). By controlling this dimensional parameter, the Ti layer provides sufficient adhesion while minimizing its impact on photo carrier transport, thus balancing adhesion improvement with photosensitivity maintenance.
Solution Approach 2:
The electrode structure is designed with different layers having different local functions: the Ti layer specifically provides adhesion at the contact interface, while the Au layer provides conductivity and chemical stability. This local differentiation allows each layer to optimize its specific function without compromising the overall device performance.
3Reliability
If electrode material with high work function is used for p-type Mg2Si, then energy barrier is reduced, but adhesion may deteriorate
Solution Approach 1:
The Ti adhesion layer serves as an intermediary that bridges the work function mismatch between the high work function electrode material and the p-type Mg2Si. This intermediate layer facilitates both good adhesion and reduced energy barrier for photo carrier collection.
Solution Approach 2:
The multi-layer electrode structure creates a composite material system where different layers address different requirements: the Ti layer optimizes adhesion and work function matching, while the Au layer provides overall electrode stability and conductivity, achieving a balance between adhesion and photo carrier collection efficiency.
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
Significantly improves the collection efficiency of photo carriers, particularly electron holes, leading to enhanced photocurrent and adhesion between the electrode and Mg2Si, resulting in improved overall performance and durability of the photodiode.
Implementation Method 1
the material that is in contact with p-type magnesium silicide is a material which has a work function of 4.81 eV or more and can react with silicon to form a silicide or can form an alloy with magnesium
Implementation Method 2
the material that is in contact with p-type magnesium silicide is a material which has a work function of 4.81 eV or more and can react with silicon to form a silicide or can form an alloy with magnesium
Implementation Method 3
devices that are sensitive to optical input signals include those having elements that convert the optical signals into electrical signals capable of being processed electronically
Data Source
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AI summary
Provided is a semiconductor photodiode which has an electrode structure having not only high adhesion to a Mg2Si material but also improved overall performance including photosensitivity. A photodiode comprising: a pn junction of a magnesium silicide crystal; an electrode comprising a material that is in contact with p-type magnesium silicide; and an electrode comprising a material that is in contact with n-type magnesium silicide, wherein the material that is in contact with p-type magnesium silicide is a material which has a work function of 4.81 eV or more and reacts with silicon to form a silicide or form an alloy with magnesium.