IMEC has developed an innovative and robust GaN-on-Si double heterostructure FET (field effect transistor) architecture for GaN-on-Si power switching devices. The architecture, announced during the recent International Electron Devices Conference (IEEE IEDM 2009), meets the normally-off requirements of power switching circuits and features low leakage and high breakdown voltage—both essential parameters to reduce the power loss of high-power switching applications.
Traditionally, high-voltage power devices are based on Si-MOSFET structures. However, for a number of applications, Si power devices have reached the intrinsic material limits. GaN-compounds, featuring high band gap and electrical breakdown field, are nowadays the best candidates to replace Si power devices. But GaN power devices are expensive. GaN epilayers grown on large diameter Si wafers, potentially up to 200mm, offer a lower cost technology compared to other substrates.
Growing a SiN/AlGaN/GaN/AlGaN double heterostructure FET structure on a Si substrate, IMEC was able to achieve a high-breakdown voltage of almost 1kV and a low on-resistance. By combining this double heterostructure FET architecture with in-situ SiN grown in the same epitaxial sequence as the III-nitride layers, IMEC succeeded in obtaining e-mode device operation. This is typically required in applications for safety reasons. The fabrication is based on an optimized process for the selective removal of in-situ SiN. The resulting SiN/AlGaN/GaN/AlGaN double heterostructure FET is characterized by a high breakdown voltage of 980V and features excellent uniformity.
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IMEC’s GaN-on-Si double heterostructure FET architecture for power switching devices meets the normally-off requirements of power switching circuits and features low leakage and breakdown voltage capability of about 1kV.
