At the IEEE IEDM 2021 (International Electron Devices Meeting) in December, the Belgian nanoelectronics research center Imec demonstrated the co-integration of high-performance Schottky barrier diodes and depletion-mode HEMTs on a p-GaN 200-V GaN-on-SOI platform with 200-mm substrate. This combination enables higher functionality and performance for GaN power ICs and monolithic integration of the power circuits with the driver functions. The result is smaller, faster and more efficient DC/DC converters and point-of-load converters.
Integration on 200-mm GaN-on-SOI substrate: E-mode p-GaN HEMT (A), D-mode HEMT (B), Schottky barrier diode (C)One of the main obstacles to the achievable higher performance of GaN power ICs so far is the lack of p-channel GaN devices for CMOS technology built with p- and n-type FETs (field-effect transistor). In GaN, the mobility of the holes is 60 times lower than that of the electrons. A p-channel device would therefore be 60 times larger than its n-channel counterpart. One alternative is to replace the P-MOS with a resistor based on the RTL principle (Resistor Transistor Logic), which involves compromises in terms of switching time and power consumption.
"We improve the performance of GaN ICs by combining enhancement-mode and depletion-mode switches. By adding D-mode HEMT to E-mode HEMT on SOI, we can move from RTL to direct-coupled FET logic, which increases speed and reduces power consumption," explains Stefaan Decoutere, program director for GaN power systems at Imec. The use of the GaN Schottky barrier diode results in higher reverse voltages and lower switching losses compared to Si devices.
"The new GaN IC platform is available for prototyping in Imec's MPW (multi-project wafer) service," explains Decoutere. "We are on the lookout for foundries, design houses and end-users." A 650 V version of the platform is in preparation. Target applications for this GaN-on-SOI technology are high-voltage power switches and converters, fast charging of cell phones and laptops, including in electric vehicles, and inverters for solar panels on the power grid.
