Speaker： Dr. Atsushi Nishikawa,ALLOS Semiconductors GmbH
GaN-on-Si HEMTs are very attractive for power device applications. However, large lattice constant and thermal expansion coefficient mismatch between GaN and Si cause low crystal quality of GaN, which limits the isolation of GaN. To resolve the poor isolation issue, carbon doping is typically applied to some parts of the GaN structure. However, carbon doping causes negative side effects like a deterioration of dynamic Ron and a further drop of crystal quality. Therefore, we have developed GaN-on-Si growth technologies with epitaxial lateral overgrowth and interlayers for crystal quality improvement for high isolation without carbon doping and precise strain-engineering. As a result, we have successfully obtained 7 μm thick and high crystal quality GaN layer on Si substrate. GaN-on-Si HEMTs show vertical and lateral grounded leakage current as low as 0.003 μA/mm2 and 0.007 μA/mm at 600 V, respectively. Physical breakdown does not occur up to 1200 V. The critical electric field derived from lateral floating current-voltage measurements is as high as 1.7 MV/cm, which is much higher than typically reported values (< 1.0 MV/cm). Good switching performance is determined by a dynamic Ron ratio of less than 1.25 up to negative bias of 600 V. These results open the way to use GaN-on-Si for high power device applications even without carbon doping. Latest results show an extension to higher voltage operation beyond 1200 V.
Dr. Atsushi Nishikawa is Chief Technology Officer of ALLOS Semiconductors GmbH, an international IP licensing and developing company for GaN-on-Si patents and technology. Nishikawa has more than 15 years’ experience in MOCVD growth of III-nitride. Prior to co-founding ALLOS he was head of epitaxy at GaN-on-Si pioneer AZZURRO Semiconductors and worked in GaN-related research at NTT Basaic Research Labs and Osaka University. At ALLOS he continues to head the advancement of the technology as well as the transfer of ALLOS’ GaN-on-Si technology to its customers’ reactors.