Heterojunction LED with Layer-Transferred GaN and Amorphous SiC Injection
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Solution Overview
Problem
Wide bandgap light emitting diodes (LEDs) are expensive and require high temperatures for epitaxial growth, making them incompatible with low-cost and flexible substrates, while low-temperature alternatives like organic LEDs suffer from short lifetimes and a-SiC:H p-i-n LEDs have excessive non-radiative recombination due to defects in amorphous materials.
Innovation Solution
A method involving a monocrystalline III-V emissive layer transferred from a host substrate to a handle substrate using a layer transfer technique, replacing conventional amorphous emissive layers with crystalline GaN and using low-temperature PECVD-grown a-SiC:H injection layers to eliminate non-radiative recombination and reduce substrate costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If wide bandgap materials are used for LED emission, then emission efficiency and device performance are improved, but manufacturing cost increases and high-temperature epitaxial growth is required
Solution Approach 1:
The device is segmented into distinct functional layers: a monocrystalline III-V emissive layer for efficient light emission, and amorphous silicon carbide injection layers for carrier injection. This segmentation allows each layer to be optimized independently - the emissive layer uses wide bandgap material for high efficiency while the injection layers use low-cost amorphous material that can be deposited at lower temperatures
Solution Approach 2:
Amorphous silicon carbide injection layers serve as intermediary layers between the metal contacts and the monocrystalline III-V emissive layer. These intermediary layers enable carrier injection into the wide bandgap emissive material without requiring the entire structure to withstand high-temperature epitaxial growth, thus reducing manufacturing costs while maintaining emission efficiency
2Loss of energy
If wide bandgap materials are used for LED emission, then emission efficiency is improved, but process temperature requirements increase
Solution Approach 1:
The device structure separates the high-performance emissive function from the low-temperature processing requirements by using different material systems in different layers. The monocrystalline III-V emissive layer provides high emission efficiency, while the amorphous silicon carbide injection layers can be deposited at lower temperatures using techniques like PECVD
Solution Approach 2:
The invention changes the material parameter from monocrystalline throughout to a heterostructure combining monocrystalline III-V with amorphous silicon carbide. This parameter change allows the injection layers to be processed at lower temperatures while the emissive layer maintains its high efficiency through monocrystalline structure
3Ease of manufacture
If amorphous emissive layers are used to reduce cost, then manufacturing cost decreases, but non-radiative recombination increases due to defects
Solution Approach 1:
Different regions of the device have different material qualities optimized for their specific functions. The emissive region uses high-quality monocrystalline III-V material with minimal defects to ensure radiative recombination dominates, while the injection regions use cost-effective amorphous silicon carbide. This local quality differentiation maintains low cost while minimizing non-radiative recombination losses
4Temperature
If organic LEDs are used for low-temperature operation, then process temperature decreases, but device lifetime decreases due to chemical quenching
Solution Approach 1:
The device uses a composite material structure combining inorganic monocrystalline III-V emissive material with inorganic amorphous silicon carbide injection layers. This composite structure provides both low-temperature processing capability (from the amorphous injection layers) and high device lifetime (from the stable inorganic emissive layer), avoiding the chemical quenching issues of organic materials
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 approach results in a cost-effective, flexible, and high-efficiency light emitting diode with reduced non-radiative recombination, suitable for applications like solid-state lighting and flexible displays.
Implementation Method 1
Wide bandgap light emitting diodes (LEDs)
Implementation Method 2
A first hot-carrier-tunneling injector (HTI) layer formed on a first side of the emissive layer
Data Source
AI summary
A method for forming a light emitting device includes forming a monocrystalline III-V emissive layer on a monocrystalline substrate and forming a first doped layer on the emissive layer. A first contact is deposited on the first doped layer. The monocrystalline substrate is removed from the emissive layer by a mechanical process. A second doped layer is formed on the emissive layer on a side from which the substrate has been removed. The second doped layer has a dopant conductivity opposite that of the first doped layer. A second contact is deposited on the second doped layer.