At this week's International Electron Devices Meeting, the nanoelectronics research center imec presents an innovative, simple and robust GaN-on-Si double heterostructure FET (field effect transistor) architecture for GaN-on-Si power switching devices. The architecture meets the normally off requirements of power switching circuits and is characterized by low leakage and high breakdown voltage, both essential parameters to reduce the power loss of high-power switching applications.
High-voltage power devices are traditionally based on Si-MOSFET structures. However, for a number of applications, Si power devices have reached the intrinsic material limits. GaN-compounds are nowadays the best candidates to replace Si power devices, thanks to their high band gap (excellent transport properties) and their high electrical breakdown field. However, the cost of GaN power devices is high. GaN-epilayers grown on large diameter Si wafers, potentially up to 200mm, offer a lower cost technology compared to other substrates.
Imec obtained a high-breakdown voltage of almost 1000V combined with low on-resistance by growing an SiN/AlGaN/GaN/AlGaN double heterostructure FET structure on a Si substrate. By combining its 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, an excellent uniformity and a low dynamic specific on-resistance of 3.5 mW.cm2 that is well within the present state-of-the-art. These results hold the promise of a huge market opportunity for GaN-on-Si power devices.
Within imec's industrial affiliation program (IIAP) on GaN-on-Si technology, imec and its partners focus on the development of GaN technology for both power conversion and solid state lighting applications. An important goal of the program is to lower GaN technology cost by using large-diameter GaN-on-Si and hence by leveraging on the scale of economics. Imec invites both integrated device manufacturers and compound semiconductor industry to join the program. Partners can build on imec's extensive expertise in GaN and benefit from sharing of cost, risk and talent.