The Role of Sapphire in LEDs


High-brightness LEDs are replacing incandescent bulbs in many architainment applications, but did you know that blue, green, and white LEDs rely upon sapphire materials for their production? At the mention of sapphire, a majority of the population might immediately conjure up images of fine jewelry; yet this very same material is a critical component in the optoelectronics industry, enabling production of high-brightness LEDs used in an increasing number of end-use applications.

Originally, in the late 80s, sapphire tended to be used for end-use military applications. Then, in the mid-90s, engineers discovered that sapphire could also be used to solve some of the challenges associated with the production of LEDs. Prior to this, researchers attempted to demonstrate devices using a zinc selenide/gallium arsenide substrate configuration, but this approach suffered from lifespan issues, and the resulting devices were not very robust or reliable. Further, sapphire was more readily available than other materials like silicon carbide, and no other material was at a comparable maturity point.

Sapphire substrates, or wafers, are now used by the majority of the world's LED manufacturers for the production of green, blue, and white LEDs. The crystalline structure of the sapphire must have a certain quality and consistency, and the wafer must adhere to precise orientation and flatness parameters. Similar to the semiconductor industry, the trend is to increase the size of the wafers to achieve cost efficiencies (i.e., more devices per wafer). Three-inch wafers are now replacing two-inch wafers, and four-inch wafers are on tap for the future. Moreover, these new wafers facilitate the production of large area displays, which rely on bigger LEDs and thereby require larger substrates.

Architainment is one of the emerging applications for LEDs, joining more long-standing applications like monochrome signaling (traffic lights, automobile tail lights, etc.), portable devices (cell phones, PDAs, etc.), signage (replacing neon signs, etc.), and large area displays (jumbotrons). As many lighting designers can attest, LEDs offer brightness and energy efficiency advantages, as well as a compact size relative to incandescent and fluorescent bulbs. Future applications include backlighting for televisions and flat screen displays (to increase the brightness and life spans of those products), flash bulbs for cell phone cameras, automotive interior lighting, running lights and eventually headlights, and other systems that require low power consumption but fast response.

Such opportunities for LEDs are evident because LEDs have the unique ability to improve light generation and light extraction while also increasing lifespan and addressing heat management issues. Look for the LED industry to continue to focus on increasing cost efficiencies, light intensity, and heat flux properties as it makes further inroads into current and future uses in entertainment.

David Reid is a product manager in the sapphire business segment of Honeywell Electronic Materials, one of the top five material suppliers to the semiconductor industry and a supplier of sapphire substrates to the optoelectronics industry. He can be reached at [email protected].