The Emcore Corp. has announced that a team, including Emcore, Group4 Labs and engineers at the U.S. Air Force Research Labs (AFRL), has demonstrated what is said to be the world's first successful fabrication of an operational gallium nitride (GaN)-on-Diamond High-Electron-Mobility-Transistor device. AlGaN/GaN epitaxial transistor layers were grown by metal-organic chemical vapor deposition at Emcore and then atomically attached to chemically vapor deposited diamond substrate by Group4 Labs. The AFRL team then fabricated the transistors.

This achievement highlights the feasibility of producing GaN-based RF devices closely thermally coupled to diamond substrates to maximize heat extraction from these devices. Until now, the leading substrate has been silicon carbide, according to Ivan Eliashevich, technical director at Emcore's Electronic Materials & Device division. However, AlGaN/GaN on diamond enables much higher power than both silicon and silicon carbide because diamond exhibits excellent thermal conduction capabilities. Whereas silicon exhibits conductivities of 130 W/M-K (Watts/meter-Kelvin), silicon carbide is at 400 W/M-K to 500 W/M-K; however diamond is at 1000 W/M-K to 2500 W/M-K—more than an order of magnitude higher than conventional silicon and considerably higher than silicon carbidel.

Cost is quite manageable for polycrystalline diamond because it is deposited using traditional chemical vapor deposition technology. Moreover, gallium nitride (GaN)-on-Diamond brings about a clear cost advantage over, for example, a 3-inch silicon carbide wafer.

The prime markets for GaN transistors are in high-power, millimeter-wave applications such as radar and spread-spectrum electronic weapons. This work was supported in part by a DARPA-funded cooperative agreement between EMCORE and AFRL.

Recently, Emcore agreed to sell its Electronic Materials & Device division to IQE, plc.

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