Enhancement-mode AlGaN/GaN HEMTs fabricated by fluorine plasma treatment

Abstract

The fabrication of enhancement-mode AlGaN/GaN HEMTs by fluorine plasma treatment on sapphire substrates is reported. A new method is used to fabricate devices with different fluorine plasma RF power treatments on one wafer to avoid differences between different wafers. The plasma-treated gate regions of devices treated with different fluorine plasma RF powers were separately opened by a step-and-repeat system. The properties of these devices are compared and analyzed. The devices with 150 W fluorine plasma treatment power and with 0.6 μm gate-length exhibited a threshold voltage of 0.57 V, a maximum drain current of 501 mA/mm, a maximum transconductance of 210 mS/mm, a current gain cutoff frequency of 19.4 GHz and a maximum oscillation frequency of 26 GHz. An excessive fluorine plasma treatment power of 250 W results in a small maximum drain current, which can be attributed to the implantation of fluorine plasma in the channel.