GaN LED Ohmic Electrode with Reflective Barrier Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gallium nitride-based semiconductor devices face issues with high operation voltage, low light output, and poor thermal stability due to increased current spreading resistance and inefficient heat dissipation, particularly in high-power LED applications, and existing p-type ohmic electrodes suffer from low reflectance and degradation at elevated temperatures.
Innovation Solution
A gallium nitride-based III-V group compound semiconductor device with an ohmic electrode layer comprising a contact metal layer, a reflective metal layer, and a diffusion barrier layer, specifically formed by laminating layers such as Ni, Ir, Pt, Ag, Ru, and Au, followed by a thermal treatment process under an oxygen atmosphere to enhance contact resistivity, reflectance, and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick p-type ohmic electrode is used to reduce current spreading resistance, then current spreading resistance decreases, but the electrode material must have both low absorbance and high reflectance which limits material selection
Solution Approach 1:
The electrode is divided into multiple functional layers: a reflective layer (Al or Ag) for high reflectance, a barrier layer (Ru, Ir, or Pt) to prevent diffusion, and a bonding layer (Ni/Au) for electrical contact. This segmentation allows each layer to optimize its specific function rather than requiring a single material to satisfy all requirements.
Solution Approach 2:
The invention uses a composite multi-layer structure combining metals with different properties: Al or Ag for reflectance, Ru/Ir/Pt for diffusion barrier, and Ni/Au for bonding. This composite approach achieves high reflectance (70% or more) while maintaining low contact resistivity and preventing material degradation.
2Illumination intensity
If Ag or Al reflective layers are deposited on Ni/Au transparent electrode, then reflectance increases to 70% or more, but electrode properties deteriorate drastically at temperature of 100°C or more
Solution Approach 1:
A barrier layer made of Ru, Ir, or Pt is inserted between the reflective layer (Al/Ag) and the bonding layer (Ni/Au). This intermediary layer prevents direct contact and diffusion between the reflective metal and the bonding metal, stopping the degradation process that occurs at elevated temperatures while maintaining high reflectance.
3Ease of manufacture
If conventional Ni/Au ohmic electrode is used, then manufacturing is simple, but contact resistivity is high and reflectance is insufficient
Solution Approach 1:
The electrode is segmented into multiple layers with distinct functions: reflective layer for optical performance, barrier layer for thermal stability, and bonding layer for electrical contact. This segmentation improves both contact resistivity and reflectance while maintaining manufacturability through standard sputtering processes.
4Ease of manufacture
If sapphire substrate is used for GaN LED, then LED structure can be formed, but heat dissipation is inefficient and thermal stability is poor
Solution Approach 1:
The invention changes the thermal parameter of the electrode structure by using metals with high thermal conductivity (Al, Ag, Ru, Ir, Pt) in the electrode layers. This increases the overall thermal conductivity of the electrode, enabling more efficient heat dissipation from the active layer while maintaining the sapphire substrate's structural benefits.
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
The proposed solution achieves low contact resistivity, high reflectance, and improved thermal stability, reducing operation voltage and increasing light output in LED devices, with the Me/Ag/Ru/Ni/Au ohmic electrode demonstrating superior performance compared to conventional Ni/Au electrodes.
Implementation Method 1
a material constituting the p-type ohmic electrode should have low absorbance and high reflectance
Implementation Method 2
forming an ohmic electrode layer comprising a contact metal layer, a reflective metal layer, and a diffusion barrier layer
Data Source
AI summary
The present invention relates to a gallium nitride-based compound semiconductor device and a method of manufacturing the same. According to the present invention, there is provided a gallium nitride-based III-V group compound semiconductor device comprising a gallium nitride-based semiconductor layer and an ohmic electrode layer formed on the gallium nitride-based semiconductor layer. The ohmic electrode layer comprises a contact metal layer, a reflective metal layer, and a diffusion barrier layer.