| Although AlGaN/GaN high-electron mobility transistors (HEMTs) power characteristics of microwave devices made great progress, because the lack of p-channel of the AlGaN/GaN HEMTs, similar to the CMOS circuit components can not be achieved. Usually, the threshold voltage(VT)of the AlGaN/GaN HEMTs depends on the design of the epitaxial structure, namely, the Al composition, Si doping concentration, and the thickness of the AlGaN barrier. Methods that can further modify the threshold voltage during the device fabrication stage will provide additional flexibilities in device fabrication and circuit applications. In this work, we fabricated a high-performance thin barrier Enhancement-mode (E-mode) HEMTs combined with ?uorine plasma treatment.Firstly, the characteristics of devices and material properties with different barrier thickness are analyzed. Thin barrier structure device shows better DC characteristics, especially the larger transconductance and higher threshold voltage. So, thin barrier material is becoming a candidate for fabrication E-mode HEMTs.Secondly, E-mode HEMTs are fabricated and their characteristics are measured compared with D-mode HEMTs. The E-HEMTs with ?uorine plasma treatment showed a higher VT (1.3V) compared to D-HEMTs with lower VT (–1.7V).The E-mode HEMTs exhibit smaller transconductance and current compared to the D-mode devices, due to the incomplete recovery of the plasma induced damage which causes mobility reduction.To further enhance the performance of enhanced device, the effects of different annealing temperature on device performance are studied. After rapid thermal annealing, compared with annealing effects on D-mode device,there are mainly two differences:1)After annealing the current and transconductance increase,because annealing caneffectively restore plasma-enhanced devices induced damage and increase themobility.2)The gate current keep constant.The plasma treatment may form aninsulating surface layer that blocks leakage current. |
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