GaN-on-Si device opens market

IMEC has produced 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 characterised 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, due 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 200 mm, offer a lower-cost technology compared with other substrates.

IMEC obtained a high-breakdown voltage of almost 1000 combined with low on-resistance by growing an SiN/AlGaN/GaN/AlGaN double heterostructure FET structure on an 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 obtained an e-mode device operation. This is typically required in applications for safety reasons. The fabrication is based on an optimised process for selectively removing in-situ SiN. The resulting SiN/AlGaN/GaN/AlGaN double heterostructure FET is characterised by a high breakdown voltage of 980, good uniformity and a low dynamic specific on-resistance of 3.5 mW/cm².

The results hold the promise of a huge market opportunity for GaN-on-Si power devices.

IMEC and its partners are focusing 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 technlogy cost by using large-diameter GaN-on-Si.