Nitride Semiconductor Light-Emitting Element With Graded Electron Injection
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Solution Overview
Problem
In nitride semiconductor light-emitting elements with a multiple quantum well structure, the overflow of holes from the light-emitting layer into the n-side layer occurs when using AlGaN or InGaAlN as barrier layers, leading to decreased current-luminous efficiency and power-luminous efficiency, especially at high operating current densities.
Innovation Solution
A nitride semiconductor light-emitting element configuration is implemented with a first n-type nitride semiconductor layer, a second n-type nitride semiconductor layer, an n-type electron-injection layer, and a p-type nitride semiconductor layer, where the average n-type dopant concentration of the second n-type nitride semiconductor layer is 0.53 times or less than the first n-type layer, and the n-type electron-injection layer's concentration is 1.5 times or more than the second n-type layer, enhancing luminous efficiency at high current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If AlGaN or InGaAlN barrier layers are used in the multiple quantum well structure, then the band gap energy difference between quantum well layer and barrier layer increases, but hole overflow into the n-side layer occurs leading to decreased current-luminous efficiency
Solution Approach 1:
An electron-injection layer is introduced as an intermediary between the n-side cladding layer and the light-emitting layer. This layer has higher electron concentration than both adjacent layers, creating electron concentration gradients that suppress hole diffusion into the n-side while maintaining efficient electron injection into the quantum well, thereby preventing energy loss from hole overflow
Solution Approach 2:
The patent changes the electron concentration parameter by creating a graded structure: the electron-injection layer has electron concentration higher than the n-side cladding layer (by 1×10^17 to 1×10^19 cm^-3) and higher than the quantum well layer (by 5×10^16 to 5×10^18 cm^-3). This parameter gradient controls carrier distribution to prevent hole overflow while maintaining luminous efficiency
2Power
If high operating current density is applied to improve output power, then the light emission amount increases, but hole overflow into the n-side layer increases leading to decreased current-luminous efficiency
Solution Approach 1:
The electron-injection layer acts as a mediator that becomes increasingly effective at high current densities. The high electron concentration in this layer creates a strong electron gradient that counteracts hole diffusion, allowing the device to operate at high power levels while maintaining efficient current-to-light conversion
Solution Approach 2:
By establishing electron concentration gradients through the electron-injection layer, the patent enables the device to sustain high operating current densities without proportional increases in hole overflow loss, thereby maintaining current-luminous efficiency even when output power is increased
3Productivity
If the n-side layer electron concentration is increased to improve electron injection, then electron injection efficiency improves, but hole overflow into the n-side layer is facilitated
Solution Approach 1:
The n-side region is segmented into three distinct layers with different electron concentrations: the n-side cladding layer, the electron-injection layer (with highest concentration), and the quantum well layer. This segmentation allows the electron-injection layer to serve dual functions: enhancing electron injection to the quantum well while simultaneously suppressing hole diffusion to the n-side through its high electron concentration gradient
Solution Approach 2:
The electron-injection layer is designed with locally optimized properties: its electron concentration is specifically higher than both the n-side cladding layer and the quantum well layer. This local quality enhancement creates favorable electron concentration gradients on both sides of the layer, improving electron injection efficiency while preventing hole overflow loss
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
This configuration improves luminous efficiency even at high operating current densities by effectively confining electrons and holes within the light-emitting layer, reducing the operating voltage, and maintaining electrostatic breakdown voltage, effectively enhancing the nitride semiconductor light-emitting element's performance.
Implementation Method 1
the average n-type dopant concentration of the n-type electron-injection layer is 1.5 times or more as high as the average n-type dopant concentration of the second n-type nitride semiconductor layer
Implementation Method 2
it is common to employ a quantum well structure in a light-emitting layer. When a voltage is applied to the nitride semiconductor light-emitting element employing the quantum well structure in the light-emitting layer, electrons and holes in the quantum well structure of the light-emitting layer are recombined to generate light
Implementation Method 3
electrons and holes in the quantum well structure of the light-emitting layer are recombined to generate light
Data Source
AI summary
Provided is a nitride semiconductor light-emitting element including in order a first n-type nitride semiconductor layer, a second n-type nitride semiconductor layer, an n-type electron-injection layer, a light-emitting layer, and a p-type nitride semiconductor layer, wherein the average n-type dopant concentration of the second n-type nitride semiconductor layer is 0.53 times or less as high as the average n-type dopant concentration of the first n-type nitride semiconductor layer, and the average n-type dopant concentration of the n-type electron-injection layer is 1.5 times or more as high as the average n-type dopant concentration of the second n-type nitride semiconductor layer.