Wide Bandgap GaN-based devices are capable of high voltage and high current operation, and feature high switching frequency that favors down-scaling of the indispensible passive components in switch-mode power converters. In addition, GaN maintains excellent semiconductor stability at high temperature and can operate at temperature much higher than allowed by the mainstream Si devices. This work focuses on utilizing and integrating the AlGaN/GaN HEMTs and rectifiers for analog and digital integrated circuits using a recently developed smart power IC platform. The demonstrated analog circuits include bootstrapped comparator, current mirror and voltage level shifter, and the digital functional blocks include NOR/NAND gates and Schmitt trigger.

Detailed characterizations of the ke...[ Read more ]

Wide Bandgap GaN-based devices are capable of high voltage and high current operation, and feature high switching frequency that favors down-scaling of the indispensible passive components in switch-mode power converters. In addition, GaN maintains excellent semiconductor stability at high temperature and can operate at temperature much higher than allowed by the mainstream Si devices. This work focuses on utilizing and integrating the AlGaN/GaN HEMTs and rectifiers for analog and digital integrated circuits using a recently developed smart power IC platform. The demonstrated analog circuits include bootstrapped comparator, current mirror and voltage level shifter, and the digital functional blocks include NOR/NAND gates and Schmitt trigger.

Detailed characterizations of the key devices including Enhancement-mode (E-mode) HEMT, Depletion-mode (D-mode) HEMT, Schottky Barrier Diode (SBD) and the Later Field Effect Rectifier (L-FER) are carried out to provide basic design library in the context of GaN smart power IC development. Several design rules are discussed for better device performance and yield.

A high-performance bootstrapped comparator operating with a single-polarity power supply is demonstrated. The comparator features monolithically integrated E/D-mode AlGaN/GaN HEMTs. The tail current source uses E-mode HEMT, enabling single-polarity power supply. The input stage could be either E-mode or D-mode HEMTs to cover a wide input voltage range, while the bootstrapped loads are implemented with D-mode HEMTs. The hysteresis configuration is shown to be applicable when provided with a buffer stage. To provide mirroring function for static circuits with proper biasing and operation range, the GaN current mirror composed of D-mode HEMTs and L-FERs is also designed and demonstrated. GaN voltage level shifter is shown to deliver desirable voltage drop both for analog signal matching between functional cells, and for noise margin extension and output to input matching in digital circuits.

Similar to the GaN Direct Coupled FET Logic (DCFL) inverter, the DCFL NOR gate and NAND gate are demonstrated with integrated E/D-mode HEMTs. It is shown that the input/output voltage level matching can be achieved with voltage level shifter, in a DCFL/BFL (buffered FET logic) configuration. Furthermore, a GaN Schmitt trigger circuit was demonstrated for the first time.