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

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.