UV LED Electrode Patterning for Uniform Carrier Injection
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Solution Overview
Problem
Ultraviolet LEDs using nitride semiconductor materials with an aluminum (Al) component face challenges due to high electrical resistivity, leading to low charge carrier injection efficiency in n-type semiconductor layers.
Innovation Solution
A light-emitting device with a semiconductor laminate structure featuring a patterned first portion and a light-emitting second portion, where the first portion has a current conduction section and a patterned structure with a valley-plateau contour, enhancing charge carrier spreading and injection efficiency by controlling the distance and thickness of the current conduction section and patterned structure elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nitride semiconductor materials with aluminum component are used in ultraviolet LEDs, then the energy bandgap can be adjusted and ultraviolet light emission is achieved, but the electrical resistivity increases leading to low charge carrier injection efficiency
Solution Approach 1:
The first semiconductor layer is divided into two functional portions: a current conduction portion with high doping concentration for efficient charge injection, and a light-emitting portion with lower aluminum content for optimal light emission. This segmentation allows each portion to be optimized independently, resolving the contradiction between energy bandgap requirements and electrical conductivity.
Solution Approach 2:
Different regions of the first semiconductor layer are assigned different material compositions and doping concentrations. The current conduction portion has high nitrogen content and high doping concentration for conductivity, while the light-emitting portion has optimized aluminum content for ultraviolet emission. This local quality differentiation enables simultaneous achievement of high injection efficiency and appropriate energy bandgap.
2Productivity
If the first semiconductor layer has high aluminum content for ultraviolet emission, then the light-emitting efficiency is improved, but the electrical resistivity increases reducing charge carrier injection
Solution Approach 1:
The first semiconductor layer is segmented into a current conduction portion extending from the first contact electrode to the active layer, and a light-emitting portion. The current conduction portion has high doping concentration (1×10^18 to 1×10^19 cm^-3) for low resistance, while the light-emitting portion has optimized aluminum content (10-30 at%) for efficient ultraviolet emission. This segmentation resolves the contradiction by separating conductivity function from light emission function within the same layer.
Solution Approach 2:
The current conduction portion acts as an intermediary between the contact electrode and the light-emitting portion. It provides a low-resistance pathway for charge carriers to reach the active layer, mediating between the electrical injection requirement and the light emission requirement. The high doping concentration in this intermediary region ensures efficient charge transport without compromising the aluminum content optimization in the light-emitting region.
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
Improves charge carrier injection efficiency and light-emitting efficiency by ensuring uniform current distribution and reducing the forward bias required, resulting in enhanced internal quantum efficiency and luminous efficiency.
Implementation Method 1
enhancing charge carrier spreading and injection efficiency by controlling the distance and thickness of the current conduction section and patterned structure elements
Implementation Method 2
A light-emitting device with a semiconductor laminate structure featuring a patterned first portion and a light-emitting second portion
Data Source
AI summary
A light-emitting device includes a semiconductor laminate, a first contact electrode, and a second contact electrode. The semiconductor laminate includes a first semiconductor layer, an active layer, and a second semiconductor layer being laminated in a thickness direction. The semiconductor laminate has a first portion having a patterned structure that has a first surface constituted by the first semiconductor layer, a second surface opposite to the first surface and away from the first semiconductor layer, and a side surface interconnecting the first surface and the second surface, and a second portion being a light-emitting area. The first contact electrode is formed on the first portion, electrically connected to the first semiconductor layer and in contact with the first surface, the second surface and the side surface of the patterned structure. The second contact electrode is formed on the second portion and electrically connected to the second semiconductor layer.