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^-1are 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.