Characterization of AlGaN/GaN HEMT Devices Grown by MBE

Ammonia-MBE growth techniques were developed to allow the production of AlGaN and GaN layers suitable for electronic applications on sapphire [000] substrates. DC and RF characterization of AlGaN/GaN HEMT devices have been carried out over a temperature range from -40°C to 200°C. The devices characterized were two finger × 50 µm wide designs with measured gate lengths ranging from 1 µm to 3.5 µm. Hall and CV measurements indicate a 2DEG sheet charge density at the AlGaN/GaN heterojunction interface as high as 1.9×10¹³/cm² and 1.5×10¹³/cm² respectively. Low field mobilities in excess of 950 cm²/V×s have been measured. Room temperature measurements for a device with a gate length of 1 µm and Vds set to 10 V exhibited a pinch off voltage of -5 volts. A maximum drain current of 946 mA/mm and a peak transconductance of 160 mS/mm were also measured. The off state drain to source breakdown voltage is 33 volts. Room temperature RF characterization with Vds=10 volts indicate intrinsic device fT and fMAX to be 15.6 GHz and 49.4 GHz respectively. At maximum power dissipation and chuck temperature, the channel temperature is estimated to be >320°C.