Substrate biasing effects in a high-voltage, monolithically-integrated half-bridge GaN-Chip

This paper investigates substrate biasing effects in a monolithically-integrated half-bridge stage rated for 600 V/20 A and fabricated in a lateral AlGaN/GaN-on-Si technology. On-resistance degradation effects caused by the common substrate potential are analyzed and explained for the monolithic half-bridge stage operating in a 400 V-synchronous buck converter. The detailed analysis of an ungated TLM-structure processed on the same epitaxial stack supports the understanding of physical processes during substrate bias conditions. The findings obtained are then transferred to the half-bridge IC. Finally, mitigation techniques are discussed, and 5 MHz, 400 V-to-200 V power conversion is demonstrated at a power level of 250 W.