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 r c < 0.2 Ω mm . Mobilities of order 2500 cm 2 / V s are achieved on bilayer samples after fabrication. The devices demonstrate high transconductance g m = 400 mS / mm and high current density I ds = 1.8 A / mm . The output conductance at the bias of maximum transconductance is g ds = 300 mS / mm . The GFETs demonstrate an extrinsic f t ext and f max ext of 20 and 13 GHz , respectively and show 6 dB power gain at 1 GHz in a 50 Ω system, which is the highest reported to date.