Vertical GaN LED with Metallic Substrate for Thermal Management
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Solution Overview
Problem
High-power gallium nitride (GaN) blue light emitting diodes (LEDs) face issues with high current spreading-resistance, optical output degradation, and thermal instability due to the use of sapphire substrates, which complicates manufacturing and reduces optical efficiency.
Innovation Solution
A vertical GaN LED structure is developed with a metallic support layer, a p-type reflective film electrode, and a reflective layer to enhance light emission and heat dissipation, using a metallic substrate instead of sapphire, and high doping concentrations in the n-GaN layer to improve electrical conductivity and optical output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sapphire substrate is used for manufacturing GaN LED, then the LED can be manufactured with conventional processes, but the current spreading-resistance becomes high and optical output is degraded
Solution Approach 1:
The patent extracts the GaN LED active layer from the sapphire substrate and transfers it to a metal substrate. This separation removes the harmful effect of the sapphire substrate (high current spreading-resistance) while preserving the manufactured LED structure. The active layer is detached and re-mounted on a new substrate that provides better electrical properties.
Solution Approach 2:
The patent changes the substrate material parameter from sapphire (electrical insulator) to metal (electrical conductor). This parameter change fundamentally alters the current spreading characteristics, reducing resistance and improving optical output. The metal substrate provides excellent electrical conductivity that enables efficient current distribution across the LED chip.
2Device complexity
If a sapphire substrate is used for manufacturing GaN LED, then the LED structure can be simplified, but thermal stability is degraded due to poor heat removal
Solution Approach 1:
The patent extracts the GaN LED active layer from the thermally inadequate sapphire substrate and relocates it to a metal substrate with superior thermal conductivity. This extraction removes the thermal management problem while maintaining the LED's structural integrity and functionality.
Solution Approach 2:
The patent changes the substrate's thermal conductivity parameter by replacing sapphire with metal. This parameter change enables efficient heat dissipation from the LED active layer, improving thermal stability and allowing high-power operation without thermal degradation.
3Loss of energy
If a flip-chip packaging method is used to reduce current spreading-resistance, then the current spreading-resistance is reduced, but the manufacturing process becomes complicated
Solution Approach 1:
Instead of using the conventional flip-chip approach that requires complex packaging, the patent inverts the strategy by directly forming the LED structure on a metal substrate from the beginning. The n-type GaN layer is grown directly on the metal substrate, eliminating the need for flip-chip packaging and associated complexity while achieving low current spreading-resistance.
Solution Approach 2:
The patent performs preliminary action by pre-forming the metal substrate with appropriate electrical contacts before growing the GaN layers. This preliminary preparation of the substrate eliminates the need for subsequent complex packaging steps, as the low current spreading-resistance structure is built-in from the start rather than added later through flip-chip assembly.
4Device complexity
If light is emitted through the sapphire substrate, then the LED structure can be simplified, but optical efficiency is degraded due to light absorption in the sapphire
Solution Approach 1:
The patent extracts the light emission path from the light-absorbing sapphire substrate and redirects it through the n-type GaN layer. This extraction removes the optical loss mechanism while maintaining a relatively simple LED structure. The metal substrate does not absorb light in the visible range, enabling efficient light extraction.
Solution Approach 2:
The patent changes the optical transparency parameter of the substrate by replacing sapphire (light-absorbing) with metal (optically transparent in visible range for this configuration). This parameter change enables efficient light emission without absorption losses, improving optical efficiency while maintaining structural simplicity.
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 solution results in reduced power consumption, increased optical output by 2.5 times, and improved thermal stability, making the LEDs suitable for high-power applications with enhanced chip separation and protection.
Implementation Method 1
a metallic substrate, conductive layer substrate or conductive ceramic substrate is used, instead of a sapphire substrate, to efficiently release heat generated upon the operation of the element to the outside
Implementation Method 2
a p-type reflective film electrode is partially formed on a p-GaN in a mesh form and a reflective layer is inserted therebetween such that photons formed in an active layer can be maximally emitted toward an n-GaN layer
Implementation Method 3
high concentration of doping (>1019/cm3) into an n-GaN layer can be obtained to thereby improve electrical conductivity of n-GaN layer
Data Source
AI summary
The present invention relates to a gallium nitride (GaN) compound semiconductor light emitting element (LED) and a method of manufacturing the same. The present invention provides a vertical GaN LED capable of improving the characteristics of a horizontal LED by means of a metallic protective film layer and a metallic support layer. According to the present invention, a thick metallic protective film layer with a thickness of at least 10 microns is formed on the lateral and/or bottom sides of the vertical GaN LED to protect the element against external impact and to easily separate the chip. Further, a metallic substrate is used instead of a sapphire substrate to efficiently release the generated heat to the outside when the element is operated, so that the LED can be suitable for a high-power application and an element having improved optical output characteristics can also be manufactured. A metallic support layer is formed to protect the element from being distorted or damaged due to impact. Furthermore, a P-type electrode is partially formed on a P—GaN layer in a mesh form to thereby maximize the emission of photons generated in the active layer toward the N—GaN layer.