64% AlGaN Channel HFET With High Johnson’s Figure of Merit (>6 THz·V)

In this letter, we report a heterostructure field effect transistor (HFET) with Al0.87Ga0.13N barrier and Al0.64Ga0.36N channel grown by metalorganic chemical vapor deposition (MOCVD). TLM measurements of the structure showed a sheet resistance of <tex-math notation="LaTeX">~ ~2000~Ω </tex-math>/sq and linear ohmic contact resistance of <tex-math notation="LaTeX">4.54~Ω · </tex-math> mm. A HFET with a gate length of <tex-math notation="LaTeX">~ ~200 </tex-math> nm, source-drain spacing of <tex-math notation="LaTeX">4~μ </tex-math>m showed a peak transconductance of ~40 mS/mm and a high peak drain current of ~0.6 A/mm. A current gain cutoff frequency (f <tex-math notation="LaTeX">T) </tex-math> of 15.7 GHz and a power gain cutoff frequency of 20.4 GHz was observed. The breakdown voltage of this device is 390 V, yielding a high Johnson’s figure of merit (JFOM) of 6.1 THz <tex-math notation="LaTeX">· </tex-math> V. This JFOM value is one of the highest reported JFOM values for AlxGa <tex-math notation="LaTeX">_ 1-x </tex-math>N channel HFET (x >0.4) and also for other ultra-wide bandgap (UWBG) transistors.