GaN Power Electronic Devices Lab

GaN-based high-voltage power switching transistors and GaN Schottky diodes enable efficient power converters with increased power density. High converter switching frequencies can be realized with lateral GaN-based HFETs due the low area-specific on-state resistance for a given blocking strength and the low gate charge required for switching.

  • [+] 65 mOhm / 600 V GaN transistors (4.4 x 2.3 mm) on a 4" wafer. Small test structures are also visible.
  • [+] Section of a transistor cell with source, gate and field plate (SEM image)
  • [+]
  • [+] 100 mOhm / 600 V GaN Schottky diode in a test package

HV normally-off switching transistors

Output characteristics of a normally-off switching transistor
Output characteristics of a normally-off 65 mOhm / 600 V switching transistor
Switching transient of test transistor
600 V / 0.3 A switching transient of a small 5 Ohm test transistor

A normally-off transistor characteristic is required in power electronics applications because of inherent power-system safety requirements. FBH uses a p-type GaN gate module to convert the GaN HEMT into an intrinsic normally-off device.

Key figures of the recent devices:

  • 65 mΩ / 600 V transistor
  • 4.4 x 2.3 mm2 chip size
  • 1 V threshold voltage and 5 V gate swing
  • 110 A pulse current
  • 100 µA off-state leakage (Vds = 600 V)
  • 15 nC gate charge and 5 µJ switching energy (Eoss at 400 V)
  • dynamic Ron: 164 mΩ for 2.5 µs after 600 V off-state

Current research is focused on low dispersion devices for blocking up to 1000 V and on further increasing the threshold voltage.

HV Schottky diodes with low onset voltage

Lateral GaN based Schottky diodes with particular low onset voltage and low capacitive charge (Qrr) have been developed by using a recessed anode technology. Strong reverse blocking up to 1000 V was achieved by combination of epitaxial design and field plate design.

Key figures of the developed devices:

  • 100 mΩ / 600 V diode
  • 4.4 x 2.3 mm2 chip size
  • 0.5 V onset voltage
  • 5.5 nC capacitive charge for a 400 mΩ / 600 V diode