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GaN on Diamond

We are all aware that electronics is continually shrinking and more and more functionality is being squeezed in to an ever decreasing space. However as electronic devices are not 100% efficient, this also means that the heat generated due to losses in the devices is also dissipated in an ever decreasing area. In some instances, the power density in some modern electronic devices is as high as that on the surface of the sun. Clearly if this heat is not removed the devices would simply melt and fail. The cooling requirements for modern electronics are therefore very extreme and are often the limiting factor in how well a device can perform even if the fundamental materials properties could allow higher performance.

DiamondGraph
Fig 1. Channel temperature vs power density for a two finger GaN transistor. GaN on SiC is currently the highest performance technology available. GaN on diamond could deliver at least a 40% reduction in channel temperature for the same power density enabling either increased reliability or increased performance.

 The ability of a material to conduct heat away from the hot part of a device is described by its thermal conductivity. Diamond has a thermal conductivity of 2000W/mK, five times larger than that of copper and the highest of any material making it the ideal material to remove heat from electronic devices. Incorporating diamond heat spreaders in to semiconductor systems is very challenging though as it has very different mechanical and structural properties to most semiconductors.

 One of the most promising new semiconductor materials is Gallium Nitride (GaN). Because of its wide band gap and the ease with which electrons can move through it, GaN offer the promise of a new generation of higher power, higher efficiency and smaller electronics. GaN device technology has now reached a point where removing heat is a key limiting factor in device performance and reliability. In our new project we will be working with a group of world leading universities (Bristol, Cardiff, Glasgow, Birmingham) and companies (IQE, Element6, MACOM, Onsemi, Airbus, ESA, Selex) to develop methods to incorporate diamond in to the heart of GaN transistors. This will allow the power density in GaN devices to be increased by up to a factor of 6 over the current state of the art and will be key to enabling the next generation of radars and the development future mobile phone networks at 5G and beyond.