Avalanche Photodiode Structure With SiC Substrate Heat Dissipation
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Solution Overview
Problem
Avalanche photodiodes for optical communication applications face challenges in heat dissipation due to the use of InGaAs or InP substrates, which hinder efficient transfer of heat generated in the multiplication layer to the outside, leading to increased thermal resistance and potential element failure.
Innovation Solution
The use of a substrate with higher thermal conductivity, such as SiC, and forming layers with lattice constants matching InP, including an n-type contact layer, multiplication layer, field-control layer, absorption layer, and p-type contact layer, along with a buffer layer and n-type conductive layer, to enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If InGaAs or InP substrates are used in avalanche photodiodes, then the device can be manufactured with standard processes and lattice-matched layers, but thermal resistance increases and heat dissipation deteriorates
Solution Approach 1:
The patent introduces a heat dissipation layer made of high-thermal-conductivity material (such as diamond or SiC) as an intermediary between the InP-based active layers and the substrate. This mediator layer enables efficient heat transfer from the multiplication layer to the substrate while maintaining the lattice-matched InP structure for device fabrication, thus resolving the contradiction between ease of manufacture and thermal management
Solution Approach 2:
The patent creates a composite structure combining InP-based semiconductor layers (for optical functionality) with a heat dissipation layer of high-thermal-conductivity material. This composite approach allows the device to benefit from both the manufacturability of standard InP processes and the superior thermal properties of materials like diamond or SiC
2Speed
If element diameter is reduced to increase speed, then response speed improves, but current density increases and heat generation worsens
Solution Approach 1:
The patent applies local quality by implementing a heat dissipation layer specifically at the location of the multiplication layer where heat is generated, while maintaining the overall element structure for high-speed operation. This localized thermal management allows small-element high-speed photodiodes to dissipate heat effectively without compromising their compact design
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 configuration significantly reduces thermal resistance and temperature rise near the multiplication layer, improving heat dissipation and light input resistance in avalanche photodiodes.
Implementation Method 1
a substrate constituted of a semiconductor with higher thermal conductivity than InP
Implementation Method 2
The n-type region 304 is formed by selective ion implantation of Si (n-type impurities) with respect to the buffer layer 303
Implementation Method 3
a light-receiving element is an element responsible for converting an optical signal that is propagated through an optical fiber into an electrical signal
Data Source
AI summary
An embodiment avalanche photodiode includes a substrate, an n-type contact layer, a buffer layer, a multiplication layer, a field-control layer, an absorption layer, and a p-type contact layer. A conductive layer is formed in a central part of the buffer layer. The substrate is constituted of a semiconductor with a higher thermal conductivity than InP such as SiC, and the n-type contact layer is constituted of a same semiconductor as the substrate and is made n-type.