PERFORMANCE OF AIGaN/GaN :HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS FOR HIGH-FREQUENCY AND HIGH-POWER ELECTRONICS

Preparation and properties of GaN-based heterostructure field-effect transistors (HFETs) for high-frequency and high-power applications are studied in this work. Performance of unpassivated and SiO2 passivated AlGaN/GaN HFETs, as well as passivated SiO2/AlGaN/GaN MOSHFETs (metal-oxide-semicondutor HFETs) is compared. It is found that MOSHFETs exhibit better DC and RF properties than simple HFET counterparts. Deposited SiO2 yielded an increase of the sheet carrier density from 7.6x10(12) cm(-2) to 9.2x10(12) cm(-2) and subsequent increase of the static drain saturation current from 0.75 A/mm to 1.09 A/mm. Small-signal RF characterisation of MOSHFETs showed an extrinsic current gain cut-off frequency f(T) of 24 GHz and a maximum frequency of oscillation f(max) of 40 GHz. These are fully comparable values with state-of-the-art AlGaN/GaN HFETs. Finally, microwave power measurements confirmed excellent performance of MOSHFETs:the output power measured at 7 GHz is about two-times larger than that of simple unpassived HFET. Thus, a great potential in application of GaN-based MOSHFETs is documented.