LED Chip Contact Structure for Hole Injection and Current Spreading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LED technologies face challenges in maximizing light emission efficiency due to limited current spreading within the LED structure, particularly for larger area LEDs, which affects the extraction and external quantum efficiency.
Innovation Solution
Incorporating high work function transition metal oxide layers as part of the contact structures for epitaxial layers, combined with current spreading layers, to enhance hole mobility and transport, including materials like molybdenum oxide, tungsten oxide, and vanadium oxide, with work functions ranging from 6 to 10 electron volts, and thicknesses from 1 nanometer to 100 nanometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact structures are used for p-type epitaxial layers, then the device complexity remains low, but hole mobility and transport are insufficient
Solution Approach 1:
The patent employs composite contact structures combining multiple materials with different work functions (e.g., tungsten oxide, molybdenum oxide, vanadium oxide, indium tin oxide) to create an optimized contact interface. This composite approach enables improved hole mobility and transport by selecting materials whose work functions match the energy band structure of the p-type layer, thereby resolving the contradiction between maintaining simple structures and achieving high reliability.
Solution Approach 2:
The invention systematically varies the work function parameter of contact layer materials to optimize hole injection. By selecting materials with work functions in specific ranges (6-10 eV) and adjusting layer thicknesses (1-100 nm), the patent achieves enhanced hole mobility without significantly increasing device complexity, as these are material parameter optimizations rather than structural additions.
2Productivity
If larger surface area electrodes are used to improve current spreading, then current distribution improves, but the device complexity increases
Solution Approach 1:
The patent uses composite current spreading layers combining materials like indium tin oxide (ITO) with transition metal oxides to achieve both high electrical conductivity and improved current distribution. This material composition approach enables effective current spreading across larger areas without requiring complex electrode geometries or finger patterns, thus improving productivity while controlling device complexity.
Solution Approach 2:
The invention optimizes the electrical conductivity parameter of contact and spreading layers by selecting materials with appropriate conductivity values and adjusting layer thicknesses. This parameter optimization allows current to spread more effectively across the electrode surface without increasing structural complexity, as the improvement comes from material properties rather than geometric complexity.
3Productivity
If high work function contact layers are added to enhance hole mobility, then light emission efficiency improves, but the device complexity increases
Solution Approach 1:
The patent integrates high work function transition metal oxides (tungsten oxide, molybdenum oxide, vanadium oxide) as contact layers within the existing epitaxial structure. These materials provide the necessary work function match to the p-type layer for efficient hole injection, thereby improving light emission efficiency. The integration is achieved through standard semiconductor fabrication processes, which minimizes the increase in device complexity despite adding functional layers.
Solution Approach 2:
The invention optimizes the work function parameter of contact layers by selecting materials with work functions in the 6-10 eV range that match the energy band structure of the p-type epitaxial layer. This parameter matching enables efficient hole injection and improved light emission efficiency without requiring complex multi-layer structures, as the key improvement comes from selecting materials with appropriate electronic properties rather than adding numerous layers.
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 hole mobility and injection, reducing energy barriers and enhancing light emission efficiency by providing effective current distribution and maintaining structural integrity, thereby increasing the overall light extraction and quantum efficiency of LEDs.
Implementation Method 1
contact layer comprising a transition metal oxide... the contact layer comprises a work function in a range from 6 electron volts (eV) to 10 eV... to enhance hole mobility and transport
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and more particularly current injection structures for LED chips are disclosed. Current injection structures include integrated layers or materials with high work functions as part of contact structures for epitaxial layers of active LED structures. Exemplary structures provide high work function contact layers for p-type epitaxial layers to enhance hole mobility and transport. Further contact structures include combinations of high work function layers with other current spreading layers. Exemplary materials for high work function layers include transition metal oxides.