Group-III Nitride LED P-Type Contact Layer Design
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Solution Overview
Problem
Current group-III nitride-based light emitting diodes face challenges with low light transmittance and poor electrical characteristics due to the p-type ohmic contact layers, leading to reduced efficiency and shortened lifespan.
Innovation Solution
A p-type multi-layered ohmic contact layer is introduced, comprising thermally decomposed nitride formed by combining nitrogen with metals like nickel, copper, zinc, and indium, along with conductive oxides and reflective metals, to enhance ohmic contact and light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type ohmic contact layer is used to improve electrical characteristics, then current injection is improved, but light transmittance decreases below 80%
Solution Approach 1:
The contact layer is divided into multiple layers with different functions: a lower contact layer (Ni/NiOx) for electrical contact and an upper transparent layer (ITO) for light transmission. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The patent uses composite material structures combining different materials with complementary properties: nickel and nickel oxide for ohmic contact, indium tin oxide for transparency and conductivity. This composite approach achieves both low contact resistance and high light transmittance.
2Illumination intensity
If a high-reflective electrode material is used to improve light reflectance, then external quantum efficiency increases temporarily, but mechanical adhesion and thermal stability deteriorate
Solution Approach 1:
The patent employs composite electrode structures combining reflective materials (Al, Ag) with adhesion-promoting metal layers (Ni, Cr). This composite structure maintains high reflectance while the metal layers provide mechanical anchoring and thermal stability.
Solution Approach 2:
Metal layers such as nickel and chromium serve as intermediary layers between the reflective material and the semiconductor substrate. These intermediary layers improve mechanical adhesion and thermal stability while allowing the reflective layer to maintain its optical performance.
3Reliability
If a semi-transparent conductive thin film is used to improve current spreading, then electrical conductivity increases, but light transmittance decreases due to light absorption
Solution Approach 1:
The conductive function is segmented from the transparent function into separate layers. The lower layer (Ni/NiOx) provides conductivity and current spreading, while the upper layer (ITO) provides transparency. This segmentation eliminates the trade-off by assigning functions to different layers.
Solution Approach 2:
Different regions of the contact structure have different optical and electrical properties optimized for their specific functions. The lower contact layer has high conductivity but low transparency, while the upper layer has high transparency and sufficient conductivity, creating local quality optimization throughout the structure.
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 solution improves current-voltage characteristics and light efficiency, extending the lifespan of the semiconductor device while maintaining high brightness and external quantum efficiency.
Implementation Method 1
The p-type multi-layered ohmic contact layer includes thermally decomposed nitride. The thermally decomposed nitride is obtained by combining nitrogen (N) with at least one metal component selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), indium (In) and tin (Sn).
Implementation Method 2
the semi-transparent conductive thin film is obtained by combining a normal metal, such as nickel (Ni), with a noble metal, such as gold (Au), and then heat-treating the metal under a gas atmosphere having a pre-determined temperature.
Data Source
AI summary
Disclosed is a group-III nitride-based light emitting diode. The group-III nitride-based light emitting diode includes a substrate, an n-type nitride-based cladding layer formed on the substrate, a nitride-based active layer formed on the n-type nitride-based cladding layer, a p-type nitride-based cladding layer formed on the nitride-based active layer, and a p-type multi-layered ohmic contact layer formed on the p-type nitride-based cladding layer and including thermally decomposed nitride. The thermally decomposed nitride is obtained by combining nitrogen (N) with at least one metal component selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), indium (In) and tin (Sn). An ohmic contact characteristic is enhanced at the interfacial surface of the p-type nitride-based cladding layer of the group-III nitride-based light emitting device, thereby improving the current-voltage characteristics. In addition, since the light transmittance of the transparent electrode is improved, light efficiency and brightness of the group-III nitride-based light emitting device are also improved.