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  7 Future applications

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The past decade has witnessed tremendous progress in the development of III-nitride based light emitting diodes (LEDs) for lighting and high electron mobility transistors (HEMTs) for power applications. Sharing the same GaN-based material system, monolithic integration of HEMTs and LEDs can effectively reduce undesirable parasitics and greatly improve the system stability as well as reliability. However, there are limited reports on the monolithic integration of the two kinds of devices, probably due to the huge difference in material requirements for LEDs and transistors as well as the complexity of device fabrication. A monolithic integrated HEMT-LED device with comparable performance to stand-alone devices has been recently fabricated (Fig. 7.1) and the breakdown voltage was enhanced, without degradation of the HEMT DC performance. ⁽¹⁾

Fig. 7.1 Cross-sectional schematic of the finished HEMT-LED on sapphire substrate. The inset shows the equivalent circuit diagram of the device (left). The on-testing HEMT-LED emits blue light. The inset shows the circuit schematic of the device (right).​⁽¹⁾

The power electronics industry now deals with conversion and motion, and thus requires lighter/smaller, cheaper and more efficient systems. This evolution starts with improvements at the semiconductor level, and there are four technologies which are best suited to handle new system requirements: silicon IGBT, Super Junction (SJ) MOSFETs, Gallium Nitride (GaN) and Silicon Carbide (SiC)-based devices.

GaN and SiC also have a chance to outdo silicon performance and enhance inverter capabilities. However, materials are still expensive and the technology is not yet ready. On the other hand, both of these materials can benefit from their developed status in the LED industry, and we have seen plenty of LED players paying attention to the opportunity  that power electronics represent.

Fig. 7.2 Technology positioning depending on voltage range and system value requirements (source: Yole  Développement)

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