Resistance analysis and device design guideline for graphene RF transistors

Graphene has attracted enormous attention in recent years because of its high carrier mobility and saturation velocity. High-performance graphene transistors for radio-frequency (RF) applications are especially attractive. Synthesis of high quality graphene sheets and application of various materials for gate dielectrics and substrates have been demonstrated. However, very few studies have been performed on the effects of graphene transistor parameters, such as parasitic resistances and graphene quality, in relation to RF applications. Here we report a systematic study of those effects on electrical performance depending on the transistor structure. It is found that the access resistance and contact resistance are the dominant factors leading to degradation of the device performance, especially in deep scaled devices. A guideline for device structural parameter design for required RF performance is discussed. Furthermore, we demonstrate that the newly proposed self-aligned structure can minimize access resistance component, resulting in 6 times higher cut-off frequency compared to that of the conventional structure, when the gate length is 50 nm. The findings of this study can be used to predict the device RF performance and thus help the design of graphene transistor structures to meet specific requirements.