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We report experimental demonstration of a right-angle black phosphorus (BP) tunneling field effect transistor (TFET). This device utilizes the effective mass anisotropy between the armchair (AC) and zigzag (ZZ) crystal orientations in BP as a means of inducing asymmetry between source and drain tunneling. As a result of this asymmetry, the BP TFET displays a higher ${I}_{ \mathrm{\scriptscriptstyle ON}} / {I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio by 2 orders of magnitude and steeper SS than BP TFETs oriented along either the AC or ZZ direction only. [ABSTRACT FROM AUTHOR]

Precise measurements of the mobility anisotropy along high-symmetry crystal axes in black phosphorus (BP) MOSFETs are reported. Locally back-gated BP MOSFETs with 13-nm HfO2 dielectric and channel length ranging from 0.3 to 0.7 $\mu \text{m}$ are fabricated. A single BP flake of a uniform thickness is exfoliated and etched along armchair (AC) and zigzag (ZZ) crystal axes, and the orientations are confirmed using optical and transmission electron microscopy analyses. The hole and electron mobilities along each direction are extracted using the transfer length method. The AC-to-ZZ hole mobility ratio is found to increase from 1.4 (1.5) to 2.0 (2.9) as the sheet concentration increased from $5.1\times 10^{\textsf {11}}$ to $1.9\times 10^{\textsf {12}}$ cm−2 at room temperature (77 K). The room-temperature electron mobility anisotropy is found to be similar to that for holes with an AC-to-ZZ mobility ratio increasing from 1.4 to 2.1 from $5.1\times 10^{\textsf {11}}$ to $1.9\times 10^{\textsf {12}}$ cm−2 though electrons showed only a very weak temperature dependence. A Boltzmann transport model is used to explain the concentration- and temperature-dependent mobility anisotropies which can be well described using a charge center scattering model. [ABSTRACT FROM AUTHOR]

We report high performance, orientation-controlled, and locally back-gated black phosphorus (BP) n-MOSFETs and p-MOSFETs with titanium and permalloy contacts, respectively. Devices with channel length ranging from 0.3 to 0.7~\mu \textm are analyzed. Armchair-oriented BP p-MOSFETs (n-MOSFETs) display 3.5 times (1.5 times) higher maximum current compared with zigzag devices. Saturated transconductance values up to 4.8 times (1.6 times) higher for BP p-MOSFETs (n-MOSFETs) oriented along the armchair direction compared with the zigzag direction are observed. Using this orientation control and contact engineering, n-MOSFETs with transconductance of 110~\mu \textS/\mu \textm and p-MOSFETs with contact resistance as low as 0.31 \textk\Omega \cdot \mu \textm are demonstrated. [ABSTRACT FROM AUTHOR]