Ambipolar transport in van der Waals black arsenic field effect transistors.

Black arsenic (BAs) is an elemental van der Waals semiconductor that is promising for a wide range of electronic and photonic applications. The narrow bandgap and symmetric band structure suggest that ambipolar (both n- and p-type) transport should be observable, however, only p-type transport has been experimentally studied to date. Here, we demonstrate and characterize ambipolar transport in exfoliated BAs field effect transistors. In the thickest flakes (∼ 80 nm), maximum currents, I max , up to 60 μA μm-1 and 90 μA μm-1 are achieved for hole and electron conduction, respectively. Room-temperature hole (electron) mobilities up to 150 cm2 V-1 s-1 (175 cm2 V-1 s-1 ) were obtained, with temperature-dependence consistent with a phonon-scattering mechanism. The Schottky barrier height for Ni contacts to BAs was also extracted from the temperature-dependent measurements. I max for both n- and p-type conductivity was found to decrease with reduced thickness, while the ratio of I max to the minimum current, I min , increased. In the thinnest flakes (∼ 1.5 nm), only p-type conductivity was observed with the lowest value of I min = 400 fA μm-1 . I max /I min ratios as high as 5 × 105 (5 × 102 ) were obtained, for p- (n-channel) devices. Finally, the ambipolarity was used to demonstrate a complementary logic inverter and a frequency doubling circuit.