Bottom-gate coplanar graphene transistors with enhanced graphene adhesion on atomic layer deposition Al_2O_3

摘要

A graphene transistor with a bottom-gate coplanar structure and an atomic layer deposition (ALD) aluminum oxide (Al_2O_3) gate dielectric is demonstrated. Wetting properties of ALD Al_2O_3 under different deposition conditions are investigated by measuring the surface contact angle. It is observed that the relatively hydrophobic surface is suitable for adhesion between graphene and ALD Al_2O_3. To achieve hydrophobic surface of ALD Al_2O_3, a methyl group (CH_3)-terminated deposition method has been developed and compared with a hydroxyl group (OH)-terminated deposition. Based on this approach, bottom-gate coplanar graphene field-effect transistors are fabricated and characterized. A post-thermal annealing process improves the performance of the transistors by enhancing the contacts between the source/drain metal and graphene. The fabricated transistor shows an I_(on)/I_(off) ratio, maximum transconductance, and field-effect mobility of 4.04, 20.1 μS at V_D = 0.1 V, and 249.5 cm~2/V•s, respectively.