Multilayer AlGaN UV Detector Band Gap Engineering
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Solution Overview
Problem
Current light detection devices face issues with current flow resistance due to abrupt energy band gap changes between buffer and light absorption layers, leading to reduced light detection efficiency and yield, particularly in UV light detection applications.
Innovation Solution
A multilayer band gap change layer with different energy band gaps is introduced between the buffer and light absorption layers, along with a Schottky layer made of ITO for improved light permeability and a top layer of p-InzGa1-zN doped with Mg to facilitate Schottky junction formation, and a Schottky fixing layer to prevent peeling during wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an AlN buffer layer is used between the GaN buffer layer and the AlGaN light absorption layer to prevent cracks, then the structural reliability is improved, but the light detection reaction is reduced due to the high energy band gap and insulating properties of the AlN layer
Solution Approach 1:
The AlN buffer layer is divided into multiple sub-layers with different thicknesses and compositions. The first AlN sub-layer has a thickness of 5-20 nm, the second AlN sub-layer has a thickness of 20-50 nm, and a third AlN sub-layer may be added with specific thickness. This segmentation reduces the overall insulating effect while maintaining crack prevention capabilities.
Solution Approach 2:
The buffer structure uses a composite of multiple materials including GaN, AlN, and AlGaN layers with varying compositions. The AlGaN layer has aluminum content gradually increasing from bottom to top (5-15%, 15-30%, 30-50%), creating a graded composite structure that transitions between materials to reduce abrupt band gap changes and maintain both structural integrity and detection efficiency.
2Productivity
If the Al content of the AlGaN light absorption layer is increased to 15% or higher with thickness of 0.1 μm or larger to improve light absorption, then the light absorption efficiency is improved, but cracks are produced due to differences in lattice mismatch and thermal expansion coefficient
Solution Approach 1:
The light absorption layer is segmented into multiple AlGaN sub-layers with progressively increasing aluminum content (5-15%, 15-30%, 30-50%). Each sub-layer has controlled thickness to prevent crack formation while maintaining overall light absorption efficiency. This gradual transition prevents abrupt lattice mismatch.
Solution Approach 2:
The aluminum content parameter is gradually changed from bottom to top of the light absorption layer, creating a graded composition structure. This parameter gradient allows the structure to accommodate lattice mismatch and thermal expansion differences while maintaining high light absorption efficiency through optimized thickness and composition control.
3Reliability
If the thickness of the light absorption layer is reduced to 0.1 μm or less to prevent cracks, then the crack formation is reduced, but the light absorption efficiency is deteriorated
Solution Approach 1:
Instead of using a single thin layer, the light absorption function is distributed across multiple AlGaN sub-layers with different aluminum contents and thicknesses. The cumulative thickness of all sub-layers provides sufficient light absorption, while each individual sub-layer remains thin enough to prevent crack formation.
Solution Approach 2:
The multi-layer composite structure with varying aluminum contents creates a graded index material that enhances light absorption efficiency through reduced reflection and improved optical field distribution, allowing thinner overall structure while maintaining or improving absorption performance.
4Ease of manufacture
If a Schottky junction type device is used for UV light detection due to simple fabrication process, then the ease of manufacture is improved, but the contact resistance is high and uniform Schottky junction characteristics cannot be obtained when Al content is 15% or higher
Solution Approach 1:
The Schottky junction is formed locally on specific regions of the top AlGaN layer with optimized aluminum content (30-50%). The electrode structure is designed with specific geometry and material composition to achieve uniform contact characteristics. This localized optimization allows simple fabrication while achieving precise and uniform Schottky junction properties.
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 enhances current flow and crystalline characteristics, improving the reliability and yield of light detection devices by minimizing abrupt energy band gap changes and maintaining efficient light absorption, while preventing peeling and stress-related issues.
Implementation Method 1
current flow resistance due to an abrupt energy band gap change between a buffer layer and a light absorption layer
Implementation Method 2
a Schottky layer made of ITO for improved light permeability
Implementation Method 3
a top layer of p-InzGa1-zN doped with Mg to facilitate Schottky junction formation
Data Source
AI summary
A light detection device includes a substrate, a buffer layer disposed on the substrate, a first band gap change layer disposed on a portion of the buffer layer, a light absorption layer disposed on the first band gap change layer, a Schottky layer disposed on a portion of the light absorption layer, and a first electrode layer disposed on a portion of the Schottky layer.