Metallic Substrate Nanowire LED Light Reflection
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Solution Overview
Problem
Current light-emitting diode (LED) production using sapphire or silicon carbide substrates faces issues such as lattice mismatch, non-homogeneous current injection, light emission in all directions leading to loss, and poor heat dissipation causing rapid degradation, which limits the reliability and efficiency of the devices.
Innovation Solution
A method involving the growth of semiconductor nanowires directly on a metallic substrate that reflects light, with a conductive contact area formed on the wires, using a metal or metal alloy substrate like aluminum, silver, or stainless steel, and optionally a catalyst layer and encapsulation, to enhance light reflection and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire or silicon carbide substrates are used for LED production, then the device structure is simple and manufacturing is routine, but lattice mismatch induces high dislocation rates, current injection is non-homogeneous, light loss is significant, and heat dissipation is poor leading to rapid degradation
Solution Approach 1:
A metallic substrate layer is introduced as an intermediary between the heat source and the LED structure. This metallic layer serves multiple functions: it provides excellent thermal conductivity for heat dissipation, high electrical conductivity for current distribution, and light reflection capability to reduce light loss. The metal substrate acts as a mediator that simultaneously addresses thermal management, electrical performance, and optical efficiency issues that arise from using conventional sapphire or silicon carbide substrates
Solution Approach 2:
The invention employs a composite structure combining metal substrate with semiconductor layers. The metal substrate (such as aluminum, copper, or stainless steel) is combined with semiconductor layers to form a hybrid device architecture. This composite approach leverages the superior thermal and electrical conductivity of metals while maintaining the light-emitting properties of semiconductors, thereby improving overall device reliability and performance
2Temperature
If sapphire substrate is used, then manufacturing process is routine, but thermal conductivity is low (35-40 W/mK) causing significant heating and rapid material degradation
Solution Approach 1:
The invention changes the thermal conductivity parameter of the substrate by replacing sapphire (35-40 W/mK) with metallic materials that have significantly higher thermal conductivity. For example, aluminum substrates can achieve thermal conductivity values exceeding 200 W/mK, while copper can reach over 400 W/mK. This parameter change enables more efficient heat dissipation, preventing excessive temperature rise and thereby improving material durability and device reliability
3Reliability
If sapphire substrate is used, then the substrate is electrically insulating requiring additional doped semiconductor layers for ground plane, but this increases device complexity and reduces electrical conductivity
Solution Approach 1:
The metallic substrate serves as an intermediary that simultaneously provides electrical conductivity, thermal management, and mechanical support. By using the metal substrate as the base layer, the invention eliminates the need for additional doped semiconductor layers that would be required to create a ground plane on insulating sapphire substrates. This reduces device complexity while improving electrical conductivity throughout the structure
4Illumination intensity
If active layer emits light in all directions, then light emission is omnidirectional, but approximately half of the light is lost when emitted toward the rear face
Solution Approach 1:
The invention converts the harmful effect of light emission toward the rear face (which would normally be lost) into a beneficial effect by using the metallic substrate's high reflectivity. The metal substrate reflects the rearward-emitted light back through the active layer toward the front face, converting what would be energy loss into useful light output. This significantly improves overall light emission efficiency by utilizing the reflective property of the metallic substrate
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 improves light emission directionality, reduces light loss, and enhances heat dissipation, leading to increased reliability and efficiency of the light-emitting microelectronic devices by using a metallic substrate to reflect emitted light and manage heat effectively.
Implementation Method 1
said metal support being able to reflect said light radiation
Implementation Method 2
the thermal conductivity of sapphire substrates generally being of the order of 35 to 40 W/mK
Implementation Method 3
wires based on one or more semiconductor materials capable of emitting light radiation
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C~2D
AI summary
The invention concerns a process of making a microelectronic light-emitting device, including the steps of: a) growth on a metallic support of multiple wires based on one or more semi-conducting materials designed to emit radiant light, b) formation of at least one electrical conducting zone of contact on at least one of said wires.