Figure 2. Mobility and stability of the BN–BP–BN heterostructure devices.

(a) The I–V_ds curves obtained at different gate voltages at 1.7 K. The inset is the optical image of Sample A with the following geometrical parameters: L₁₄=16 μm, L₂₃=10 μm and W=3 μm. (b) The resistivity determined from four-terminal (green line) and two-terminal configurations (orange line) at 1.7 K. (c) Variation of the contact resistivity. (d) The conductivity of Sample A measured at with a room temperature and 1.7 K. The inset shows the ambipolarity of the BP conductance. (e,f) Temperature dependence of the field-effect μ_F (open dots) and Hall mobilityμ_h (solid dots) at V_g=−70 V) of Sample A and Sample B (15 nm thick). The dashed lines serve as guidelines for the μ∼T^−γ relation. (g) The room temperature conductivity showing no hysteresis in Sample A. (h) The mobility and on–off ratio of Sample A as a functions of ambient exposure time. No quality degradation is observed even after exposure for an entire week.