Assessment of H-intercalated graphene for microwave FETs through material characterization and electron transport studies

Epitaxial graphene is grown on semi-insulating (SI) 4H-SiC in a hot wall CVD reactor by graphitization and in-situ intercalation with (H)ydrogen. A holistic material characterization is performed in order to ascertain the number of layers, layer uniformity, and electron transport properties of the epi-layers via electronic test structures and Raman spectroscopy. Bilayer graphene field effect transistors (GFETs) are fabricated using a full electron beam lithography (EBL) process which is optimized for low contact resistances of rc<0.2Ωmm. Mobilities of order 2500cm2/Vs are achieved on bilayer samples after fabrication. The devices demonstrate high transconductance gm=400mS/mm and high current density Ids=1.8A/mm. The output conductance at the bias of maximum transconductance is gds=300mS/mm. The GFETs demonstrate an extrinsic ftext and fmaxext of 20 and 13GHz, respectively and show 6dB power gain at 1GHz in a 50Ω system, which is the highest reported to date.