Reduction of leakage current by O2 plasma treatment for device isolation of AlGaN/GaN heterojunction field-effect transistors.

The influence of O 2 plasma treatment on the mesa-isolated region of AlGaN/GaN heterojunction field-effect transistors (HFETs) was studied. The etched surface of the undoped GaN layer was exposed to O 2 plasma generated by a plasma-enhanced chemical vapor deposition system. The current–voltage characteristics indicated that the current of the mesa-isolated region was strongly dependent on the treatment temperature. Treatment with O 2 plasma at 300 °C and 250 W for 15 min was confirmed to be the optimal condition, under which isolation current was reduced by four orders of magnitude and photovoltaic response was suppressed. The photoluminescence spectrum showed a decrease in the density of defects related to the yellow luminescence band and the occurrence of defects related to the blue luminescence band. X-ray photoelectron spectroscopy results showed the formation of Ga 2 O 3 and a possible defect of substitutional oxygen on the nitrogen site O N . AlGaN/GaN HFETs with an on/off drain current ratio of 1.73 × 10 7 were obtained, and the breakdown voltage of the mesa-isolated region increased from 171.5 to 467.2 V. [ABSTRACT FROM AUTHOR]