All-CVD graphene field-effect transistors with h-BN gate dielectric and local back gate

Introduction: Since the original experiments on exfoliated graphene a decade ago, extensive research has been performed on how to exploit graphene's unique properties, such as the low density of states, high mobility, tunable optical absorption and long spin lifetimes. However, in order to utilize graphene for practical applications, the interface between graphene and the surrounding materials must be understood and improved. We have previously shown that by using temperature- and frequency-dependent capacitance-voltage (C-V) measurements, the nature of the traps near the interface between graphene and HfO₂ can be probed [1-2]. In this work, we describe the electrical properties of all-CVD graphene field-effect transistors (gFETs) using hexagonal boron nitride (h-BN) as a gate dielectric and compare their performance with HfO₂-dielectric gFETs. Prior work on using h-BN as a dielectric for gFETs has shown that the mobility of graphene on h-BN is 3-10 times higher than graphene on SiO₂ [3]-[6]. In this work, we utilized a locally back-gated structure, which is useful to provide a one-to-one comparison between gFETs with different dielectrics. We show that h-BN gFETs have reduced hysteresis, and more positive Dirac voltages compared to the HfO₂ devices. Furthermore, border traps are observed to be present in the h-BN gated devices and the transistor performance is limited by the quality of the CVD graphene as determined by low-temperature analysis. The results provide important insight for the further improvement of highperformance gFETs using h-BN dielectrics.