Fabrication and characterization of 2D graphene and graphene nanoribbon field effect transistors

The recent discovery of graphene, a single atomic sheet of graphite, has ignited intense research activities to explore the electronic properties of this novel two-dimensional (2D) electronic system. The impressive properties such as the linear energy dispersion relation near the charge neutrality (Dirac) point in the electronic band structure, field-effect mobilities as high as 15 000 cm2/Vs and carrier velocity of ~10^8 cm/s at room temperature make graphene a possible candidate for electronic devices in the future. However, graphene has been studied mostly at low biases till date. For the application in practical devices, it is essential to investigate the high-field transport properties. In this work, fabrication and high field characteristics of 2D and nanoribbon graphene are described on back and top gated field effect transistors (FETs). Saturation has been achieved; the saturation current density for many samples were measured to be in the 1 - 2 A/mm range. Semiconducting graphene nanoribbon (GNR) FETs showing 10^4x I ON/OFF ratios are realized. The unique output characteristics of the devices are investigated and found to be the consequence of drain induced channel control. Epitaxial graphene FETs were fabricated and measured as well. Long channel saturation was demonstrated and the small signal performance was characterized. Power gain cut-off frequency as large as 16 GHz was measured.