Frequency multiplier based on back-gated graphene FETs with M-shaped resistance characteristics

The ambipolar graphene field-effect transistors (GFETs) usually exhibit Λ-shaped resistance versus gate voltage characteristics (R-V_g curve) with the n- and p-type regions switching at the neutrality points of graphene. However, M-shaped R-V_g curves were frequently observed in our back-gated GFETs without intentional doping. Here, we proposed an implementation of a frequency multiplier using the M-like shape of the R-V_g curve. We first investigated the effect of the channel length and the contact transfer length in a GFET on the shape of the R-V_g curve and then evaluated the influence of the various shapes of R-V_g curves on the performance of the frequency multiplier (including tripler and quadrupler). Finally, a frequency tripler based on a single GFET has been experimentally demonstrated. When applying a sinusoid input signal with a fundamental frequency at a suitable operation area, around 80% output signal power is concentrated at the third harmonic. The excellent output spectral purity makes GFETs with the M-shaped R-V_g curve promising candidates for the frequency multiplier.