The Importance of Refractory Metals in LEDs

LEDs, light-emitting diodes, are semiconductor light sources which come in various colors. They also have a number of important applications in diverse applications such as traffic signals, aviation, general lighting, automotive divisions and advertising.

The practicality and adaptability of LEDs has led to the development of ground-breaking text and video displays, as well the ability to remotely control electronic items, including televisions. It can also be argued that LEDs are more environmentally friendly than standard filament lights.

LED sales are predicted to equal more than 230 billion per year from 2015 onwards. It is clear therefore that LEDs are a product of the future. The construction of these pioneering materials is only made possible through the use of load resistant, high-quality components.

These component elements are often made from refractory metals due to their unique physical properties. PLANSEE plays an instrumental role in the production of these components, as detailed in this article.

The Role of Crucibles in LED Production

A required material for the production of LEDs is Sapphire. It is a material typically grown in pressed-sintered or formed crucibles made from molybdenum and tungsten at highly-elevated temperatures of about 2000°C and above.  These refractory metals are ideal for the production of crucibles due to their resistance to the extreme temperatures required in this process and the lack of risk of contamination to the sapphires.

PLANSEE also offer the appropriate heaters, hot zones, shield packs as well as a range of spare furnace parts for sapphire crystal growth. Furthermore, PLANSEE designs the ‘hot zone’ to respond to customer requirements even before their production.

Incredibly, the sapphire material from one single PLANSEE crucible can help in the production of 3,000,000 high-performance LEDs.

After the sapphire crystal is created, an epitaxial process is carried out in order to apply the semiconductor layers that produce light in LEDs to the substrate. The fine sapphire wafers measure around one square millimetre and act as a perfect substrate material.

Components for Epitaxial Processes

Using the MBE (Molecular Beam Epitaxy) process or MOCVD (Metal Organic Chemical Vapor Deposition) process the sapphire wafer is applied alongside the semiconductor layers in an LED. PLANSEE can offer components for the coating reactors that are resistant to extreme temperatures, for example molybdenum, tungsten and special alloys.

PLANSEE also works closely with clients to make sure that the components are thoroughly tested in stimulated conditions. Model based calculations are carried out in order to answer a broad range of important questions, for example ‘How would temperature distribution appear during furnace operation?’.

Boats and Coils

A reflector layer is often deposited on semiconductors and this acts to guide the dispersed light in the required direction. Evaporation boats and coils made from molybdenum, tungsten, tantalum and their alloys usually heat up the material for evaporation throughout the coating process. The evaporation boats and coils from PLANSEE are electrically conductive and offer low vapor pressures alongside high melting points.

Carrier Plates Made of Molybdenum and MoCu

Compared to conventional lighting, LEDs are three times more efficient, however, they do generate heat. PLANSEE make use of molybdenum and MoCu discs which means they can offer materials with an ideal coefficient of thermal expansion (CTE) appropriate for the CTE of the semiconductor material. The carrier plates provided by PLANSEE can be merged to the semiconductor to make sure that heat is consistently dissipated.

Phosphor Products for the LED Industry

A coating of phosphor can be inexpensively and cheaply applied to the LED to transform UV or blue light into a different color as required. The light of the LED stimulated the phosphor to produce a yellow-tinged light which can then be combined with the light of a blue LED to create attractive color temperatures.

GTP is the US associate of the PLANSEE Group and is making ground-breaking developments in the field of phosphor materials production of the LED industry. Moreover, GTP has developed novel coatings in order to prolong the useful lifespan of phosphor materials.

Heat Spreaders for High-Performance LEDs

In instances where high-performance LEDs become heated, PLANSEE’s heat spreaders aid in cooling down components. These heat spreaders are constructed from molybdenum, tungsten, Cu-MoCu-Cu, MoCu and WCu laminates.

Precision Optics

The LED is housed in a glass lens to make sure that the bundled light disperses in the appropriate direction and to assist in the protection of the semiconductor. Tool specialists at CERATIZIT have developed the forming tool used to produce these precision lenses.

This information has been sourced, reviewed and adapted from materials provided by PLANSEE High Performance Materials.

For more information on this source, please visit PLANSEE High Performance Materials.

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