RF loss reduction by a carbon-regulated Si substrate engineering in GaN-based HEMT buffer stacks

A carbon-regulated Si substrate engineering has been adopted to reduce the RF loss of GaN-based HEMT buffer stacks. By implanting the substrate with high-dose carbon, undersaturation of Si self-interstitials is formed, and the self-interstitial-assisted aluminum diffusion into the Si substrate during the growth can be significantly suppressed. Consequently, the formation of parasitic conductive channel is suppressed, and the RF loss of the buffer stacks can be reduced. By combining the substrate engineering with low-temperature growth, the RF loss of the buffer stacks is reduced to as low as 0.13 dB/mm at 10 GHz. In addition, the crystal quality of the buffer stacks grown on the regulated substrates does not degrade. This work shows a great potential for fabrication of high-quality and low-loss GaN-on-Si RF devices.