LED Quantum Well Structure for Non-Uniform Carrier Distribution
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Solution Overview
Problem
Nitride semiconductor LEDs with a multi-quantum well structure suffer from non-uniform carrier distribution, leading to reduced light emitting efficiency due to extra electrons not contributing to light emission and low recombination efficiency in the last quantum well.
Innovation Solution
A light emitting device with a quantum well and quantum barrier structure where the recombination rate of electron-hole pairs is higher in the second quantum well than the first, with a first quantum barrier allowing carrier tunneling from the second conductive semiconductor layer, and the first quantum well having a higher energy level than the second, improving carrier injection and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a multi-quantum well structure is used in the active layer, then the light emitting device can handle high current injection, but carrier distribution becomes non-uniform and light emitting efficiency decreases
Solution Approach 1:
The patent applies local quality by creating different quantum well structures at different locations within the active layer. Specifically, the first quantum well adjacent to the hole injection layer has a different composition ratio (higher indium content) compared to the second quantum well, resulting in different energy levels and recombination characteristics. This local differentiation ensures that each quantum well region optimizes carrier recombination according to the local carrier distribution, thereby maintaining high light emitting efficiency even under high current injection conditions.
2Illumination intensity
If current injection is increased to improve brightness, then more electrons are generated, but extra electrons are not confined in the active layer and do not contribute to light emission
Solution Approach 1:
The patent employs parameter changes by adjusting the composition ratio (indium content) of different quantum wells to create a gradient structure. The first quantum well has higher indium content than the second quantum well, creating different conduction band offsets and energy levels. This parameter variation optimizes electron confinement at different locations, ensuring that electrons generated under high current injection are effectively confined and utilized for light emission throughout the active layer.
3Productivity
If recombination mainly occurs in the last quantum well adjacent to the hole injection layer, then carrier recombination is concentrated, but the light emitting efficiency of that quantum well is low
Solution Approach 1:
The patent applies segmentation by dividing the active layer into multiple quantum well regions with different properties. Instead of relying on a single quantum well for recombination, the structure includes a first quantum well with higher indium content and different energy level, and a second quantum well with lower indium content. This segmentation distributes the recombination process across multiple regions, each optimized for different aspects of carrier recombination, thereby improving overall light emitting efficiency while maintaining high recombination rates.
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
Enhances light emitting efficiency by increasing the recombination rate in the second quantum well, improving brightness and maintaining color purity by reducing recombination in the first quantum well, thus enhancing overall LED performance.
Implementation Method 1
the first quantum barrier has a thickness allowing a tunneling of carriers, which are injected from the second conductive semiconductor layer, through the first quantum barrier
Implementation Method 2
An LED (light emitting device) is an element that converts electric energy into a light energy
Data Source
AI summary
Disclosed are a light emitting device, a method of manufacturing the light emitting device, a light emitting device package and a lighting system. The light emitting device includes a first conductive semiconductor layer; an active layer including a quantum well and a quantum barrier and disposed on the first conductive semiconductor layer; and a second conductive semiconductor layer on the active layer. The active layer includes a first quantum well adjacent to the second conductive semiconductor layer, a second quantum well adjacent to the first quantum well, and a first quantum barrier between the first quantum well and the second quantum well. A recombination rate of electron-hole in the second quantum well is higher than the recombination rate of the electron-hole in the first quantum well, and the first quantum well has an energy level higher than the energy level of the second quantum well.