Microwave performance of 0.25 mu m doped channel GaN/AlGaN heterostructure field effect transistor at elevated temperatures

The authors report the DC and microwave performance of a 0.25 mu m gate doped channel Al0.14Ga0.86N/GaN HFETs exhibiting a cutoff frequency of 37.5GHz and a maximum frequency of oscillations of 80.4GHz. The calculations of the Fermi level position and comparison with the expected conduction band discontinuity confirm that the channel in these transistors is doped. DC and microwave characteristics of these devices do not change much with temperature up to at least 200 and 90 degrees C, respectively.