Gallium Nitride Substrates
Inlustra's Nonpolar Gallium Nitride Substrates
An Inlustra m-plane Gallium Nitride substrate overlaid on a quarter-inch grid
Our proprietary crystal growth techniques significantly reduce the number of microscopic defects in the substrates, which will enable our customers to realize improved yields in their device production processes. We are currently offering nonpolar gallium nitride substrate sizes between 5x10 mm and 10x20 mm but will scale up the process to 2" over the next nine to twelve months.
Established Device Production Process
The device production process is broken down into four stages. The substrate must first be obtained or produced, which provides support and an atomic pattern for the thin device layers (which generate the light) that are deposited on it. During a multi-step device fabrication process the device layer-coated substrate is processed and divided into thousands of discrete devices, or dies, that are only a few hundredths of an inch across. Up to 2,000 laser diodes or 10,000-15,000 HB-LED dies fit onto a single two-inch diameter substrate. These discrete dies are then packaged, a process that includes mounting the dies to heat sinks, affixing electrical leads, and encasing the dies in transparent protective epoxy.
It's All in the Substrate
Of the four stages in the LED and laser diode value chain, the latter three are well understood from conventional semiconductor processing. GaN substrate technology, on the other hand, is sorely deficient and is the fundamental cause of most current device weaknesses. Therefore, virtually all GaN-based devices are still grown on non-GaN, or foreign substrates, such as sapphire and silicon carbide. Growing GaN on foreign substrates introduces tens of billions of microscopic defects into the device layer films that rob the devices of their efficiency, generating excessive heat in the process. While some techniques are available to reduce these defect densities to tolerable levels, high-end devices require low defect densities that only GaN substrates can practically offer. Expansion of the GaN-based device market will therefore be fundamentally limited by inadequate performance and low manufacturing yields until high-quality GaN substrates are widely available at modest prices.