Vertical Semiconductor Device With Graded Aluminum Layer
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Solution Overview
Problem
Ultraviolet light-emitting semiconductor devices face challenges in achieving a vertical form and maintaining optical output power due to substrate separation and moisture-induced oxidation, leading to reduced efficiency.
Innovation Solution
A semiconductor device structure is designed with a first and second conductive type semiconductor layer, an active layer, and a reflective layer, where the second conductive type semiconductor layer has a graded aluminum composition, and a recess is formed to enhance light extraction and current spreading, with a reflective layer surrounding the electrodes to improve light reflection and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a vertical form is realized for ultraviolet light-emitting devices, then device structure and light extraction are improved, but substrate separation and moisture-induced oxidation occur leading to reduced optical output power
Solution Approach 1:
The second conductive type semiconductor layer is divided into a first sub-layer and a second sub-layer with different aluminum compositions. This segmentation allows the first sub-layer to provide good ohmic contact with the electrode while the second sub-layer provides high light extraction efficiency, thus resolving the contradiction between vertical form structure and maintaining optical output power.
Solution Approach 2:
Different regions of the second conductive type semiconductor layer are given different aluminum compositions tailored to their specific functions: the first sub-layer (closer to electrode) has lower Al composition for electrical contact, while the second sub-layer (closer to active layer) has higher Al composition for light extraction. This local quality differentiation resolves the contradiction by optimizing each region for its specific purpose.
2Illumination intensity
If the aluminum composition in the second conductive type semiconductor layer is increased to improve light extraction, then light extraction efficiency is improved, but ohmic contact with the electrode deteriorates
Solution Approach 1:
The second conductive type semiconductor layer is segmented into two sub-layers with different aluminum compositions. The first sub-layer has lower Al composition (30-50%) to ensure good ohmic contact with the electrode, while the second sub-layer has higher Al composition (50-80%) to maximize light extraction efficiency. This segmentation resolves the contradiction by allowing each sub-layer to optimize for its specific function.
Solution Approach 2:
The aluminum composition is locally optimized within the second conductive type semiconductor layer: the region closer to the electrode (first sub-layer) has lower Al content for electrical contact, while the region closer to the active layer (second sub-layer) has higher Al content for light extraction. This local quality approach resolves the contradiction between ohmic contact and light extraction efficiency.
3Illumination intensity
If a recess is formed to enhance light extraction and current spreading, then light extraction efficiency and current spreading are improved, but device complexity increases
Solution Approach 1:
A recess is formed in the first conductive type semiconductor layer, creating a three-dimensional structure that enhances both light extraction and current spreading. The recess allows the electrode to be positioned closer to the active layer region, improving light extraction efficiency while also spreading current more effectively across the junction.
4Illumination intensity
If the reflective layer is disposed to surround the electrode, then light reflection and extraction are improved, but manufacturing complexity increases
Solution Approach 1:
The reflective layer serves multiple functions: it reflects light that would otherwise be lost, enhances light extraction efficiency, and provides a structural boundary for the device. By making the reflective layer extend beyond the electrode, it creates a mirror-like structure that improves optical performance while the extension can be formed using standard deposition processes.
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 enables the fabrication of a vertical-type semiconductor device with improved light extraction efficiency and current spreading, effectively addressing the issues of substrate separation and moisture-induced degradation, resulting in enhanced optical output power.
Implementation Method 1
a reflective layer disposed below the second electrode... the reflective layer is in contact with a bottom surface of the second sub-layer
Data Source
AI summary
Disclosed in an embodiment is a semiconductor device comprising: a semiconductor structure comprising a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; a second electrode electrically connected to the second conductive type semiconductor layer; and a reflective layer disposed under the second electrode, wherein the second conductive type semiconductor layer comprises a first sub-layer and a second sub-layer disposed between the first sub-layer and the active layer and having an aluminum (Al) composition higher than that of the first sub-layer, the reflective layer comes into contact with the lower surface of the second sub-layer, and the second electrode comes into contact with the first sub-layer.