Fabrication and characterization of GaN junctionfield effect transistors

Junction field effect transistors (JFET) were fabricated on a GaN epitaxial structure grown by metal organic chemical vapor deposition. The DC and microwave characteristics, as well as the high temperature performance of the devices were studied. These devices exhibited excellent pinch-off and a breakdown voltage that agreed with theoretical predictions. An extrinsic transconductance (g(m)) of 48 mS/mm was obtained with a maximum drain current (I-D) of 270 mA/mm The microwave measurement showed an f(T) of 6 GHz and an f(max) of 12 GHz. Both the l(D) and the g(m) were found to decrease with increasing temperature, possibly due to lower electron mobility at elevated temperatures. These JFETs exhibited a significant current reduction after a high drain bias was applied, which was attributed to a partially depleted channel caused by trapped electrons in the semi-insulating GaN buffer layer.