Assessment of H-intercalated graphene for microwave FETs through material characterization and electron transport studies
Journal article, 2015
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 Omega 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 Omega system, which is the highest reported to date.