Nitride Semiconductor Light Emitting Device with 2DEG Current Spreading
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Solution Overview
Problem
Planar nitride semiconductor light emitting devices suffer from non-uniform current distribution and low light emitting efficiency due to current crowding, leading to high operating voltage and reduced effective light emitting area, as well as vulnerability to electrostatic discharge and heat generation.
Innovation Solution
The formation of a two-dimensional electron gas (2DEG) layer by interposing an AlxGa1-xN layer between n-type GaN layers, combined with an AlN layer for enhanced piezoelectric effect and dislocation blocking, to improve current spreading and electron mobility, and the use of a high-resistant GaN layer for further boosting current spreading effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar structure with two electrodes on the same face is used, then the device structure is simple and easy to manufacture, but current distribution becomes non-uniform causing current crowding and reduced light emitting efficiency
Solution Approach 1:
The patent transitions from a planar two-electrode structure to a vertical three-electrode structure, adding a vertical dimension to current flow. The first and second n-type GaN layers are positioned at different vertical levels with the active layer between them, enabling current to flow vertically through the structure rather than laterally across a plane, thus eliminating current crowding while maintaining manufacturing simplicity
Solution Approach 2:
The AlxGa1-xN layer serves as an intermediary between the n-type GaN layers, creating a heterostructure that forms a two-dimensional electron gas (2DEG) layer. This intermediary layer has higher electron mobility and acts as a current spreading layer, distributing current uniformly across the light emitting area while the overall vertical structure maintains ease of manufacture
2Reliability
If current flows through the shortest route between electrodes, then electrical conduction is efficient, but current crowding occurs reducing the effective light emitting area
Solution Approach 1:
The patent applies local quality by creating a 2DEG layer with high electron mobility in specific regions (at the AlxGa1-xN/GaN interfaces) while maintaining standard conductivity elsewhere. This localized high-mobility region acts as a current spreading zone that distributes current across the entire light emitting area rather than concentrating it along the shortest conduction path
Solution Approach 2:
The patent uses composite material structure with AlxGa1-xN and GaN layers forming a heterostructure. The AlxGa1-xN layer has different electrical properties (higher electron mobility) compared to GaN, and their combination creates a composite structure that achieves both efficient conduction and uniform current distribution across the light emitting area
3Reliability
If high doping concentration is used in n-type nitride area to reduce resistance, then electrical conductivity improves, but crystalinity deteriorates and resistance to electrostatic discharge decreases
Solution Approach 1:
The AlxGa1-xN layer acts as an intermediary that enables high conductivity without requiring high doping concentrations in the GaN layers. The 2DEG formed at the AlxGa1-xN/GaN interface provides high electron mobility and conductivity, allowing the GaN layers to maintain lower doping levels and thus preserve their crystalinity and ESD resistance
Solution Approach 2:
The patent changes the electrical conductivity parameter by forming a 2DEG layer with high electron mobility through heterostructure design, rather than relying on high doping concentrations. This parameter change allows the n-type GaN layers to maintain low doping levels, preserving crystalinity while achieving high overall conductivity through the 2DEG channel
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 results in uniform current distribution, increased light emitting efficiency, improved resistance to electrostatic discharge, and enhanced crystalinity, leading to a high-efficient nitride semiconductor light emitting device with superior current spreading capabilities.
Implementation Method 1
the formation of a two-dimensional electron gas (2DEG) layer by interposing an AlxGa1-xN layer between n-type GaN layers
Implementation Method 2
The AlN layer employed in the invention generates a beneficial piezoelectric effect for increasing electron concentration of the 2 DEG layer
Data Source
AI summary
The invention provides a nitride semiconductor device and a manufacturing method thereof. In the invention, n-type and p-type nitride semiconductor layers are formed on a substrate, and an active layer is formed therebetween. The n-type nitride semiconductor layers include first and second n-type GaN layers disposed in the order of distance from the active layer. In addition, in the nitride semiconductor device of the invention, an AlxGal-xN layer, where 0<x<1, is interposed between the first and second n-type GaN layers, thereby forming a two-dimensional electron gas layer at interfaces of the first and second n-type GaN layers.