Graded Aluminum Clad Layer for Nitride Semiconductor Light Emitting Devices
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Solution Overview
Problem
Current semiconductor light emitting devices face challenges in increasing the band gap of the clad layer under the active layer, which affects light efficiency and reliability, particularly in nitride semiconductor-based LEDs and laser diodes.
Innovation Solution
A semiconductor light emitting device is designed with a first conductive type clad layer having an increased aluminum composition ratio, followed by an active layer and a second conductive type semiconductor layer, where the aluminum composition is gradually increased in the first clad layer to enhance the band gap and reduce lattice mismatch, thereby improving light emission characteristics and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the band gap of the clad layer is increased to improve light efficiency, then light emission efficiency is improved, but the manufacturing complexity increases due to the need for graded aluminum composition
Solution Approach 1:
The clad layer is designed with non-uniform aluminum composition, where the aluminum content varies through the thickness of the layer. The first clad layer has aluminum composition increasing from bottom to top, while the second clad layer has aluminum composition decreasing from bottom to top. This local variation in composition allows the band gap to be increased in specific regions to improve light extraction efficiency without requiring the entire device structure to be complex.
Solution Approach 2:
The invention changes the aluminum composition parameter through the clad layer thickness to achieve the desired band gap increase. By controlling the aluminum content gradient (increasing in the first clad layer, decreasing in the second clad layer), the band gap is optimized for light emission while maintaining a manageable manufacturing process using standard semiconductor fabrication techniques.
2Reliability
If the aluminum composition ratio is increased to enhance the band gap, then reverse breakdown voltage is improved, but lattice mismatch and strain increase
Solution Approach 1:
The aluminum composition is distributed non-uniformly through the clad layer structure. The first clad layer has aluminum composition increasing from bottom to top, and the second clad layer has aluminum composition decreasing from bottom to top. This gradual variation in composition allows the band gap and reverse breakdown voltage to be enhanced while minimizing abrupt lattice mismatches that would cause strain and defects.
Solution Approach 2:
The invention employs dynamic composition grading rather than fixed composition. The aluminum content changes continuously through the thickness of the clad layers, creating a gradient structure that adapts to balance the competing requirements of high reverse breakdown voltage (requiring high aluminum content) and low lattice mismatch (requiring gradual composition changes).
Data Source
AI summary
Provided is a semiconductor light emitting device. The semiconductor light emitting device comprises a first conductive type clad layer having a composition ratio of aluminum increased at a predetermined rate, an active layer on the first conductive type clad layer, and a second conductive type semiconductor layer on the active layer.