High-field 1/f noise in hBN-encapsulated graphene transistors
Résumé
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. Understanding this noise in graphene is a key towards high-performance electronics. Early investigations in diffusive graphene have pointed out a deviation from the standard Hooge formula, with a modified expression where the free-carrier density is substituted by a constant density n∆ ∼ 1012 cm−2 . We investigate hBN-encapsulated graphene transistors where high mobility gives rise to the non-linear velocity-saturation regime. In this regime, the α-noise is accounted for by substituting conductance by differential conductance 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 main differences: the first one is a strong enhancement of the Hooge parameter reflecting the hundred-times larger coupling of interband excitations to the hyperbolic phononpolariton (HPhP) modes of the mid-infrared Reststrahlen (RS) bands of hBN. The second is an exponential suppression of this coupling at large fields, which we attribute to decoherence effects. We also show that the HPhP bands control the amplitude of flicker 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.
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