High-field 1 / f noise in hBN-encapsulated graphene transistors

Low-frequency 1/f noise in electronics is a conductance fluctuation, that has been expressed in terms of a mobility ”α-noise” by Hooge and Kleinpenning. Understandingthis noise in graphene is a key towards high-performance electronics. Early investigations in diffusive graphene have pointed out a deviation from the standard Hoogeformula, with a modified expression where the free-carrier density is substituted bya constant density n∆ ∼ 1012 cm−2. We investigate hBN-encapsulated graphene transistors where high mobility gives rise to the non-linear velocity-saturation regime. Inthis regime, the α-noise is accounted for by substituting conductance by differentialconductance G, resulting in a bell-shape dependence of flicker noise with bias voltage V . The same analysis holds at larger bias in the Zener regime, with two maindifferences: the first one is a strong enhancement of the Hooge parameter reflectingthe hundred-times larger coupling of interband excitations to the hyperbolic phononpolariton (HPhP) modes of the mid-infrared Reststrahlen (RS) bands of hBN. Thesecond is an exponential suppression of this coupling at large fields, which we attributeto decoherence effects. We also show that the HPhP bands control the amplitude offlicker noise according to the graphene-hBN thermal coupling estimated with microwave noise thermometry. The phenomenology of α-noise in graphene supports aquantum-coherent bremsstrahlung interpretation of flicker noise. ; 107 ; 16