Impact of Orientation Misalignments on Black Phosphorus Ultrascaled Field-effect Transistors

Two-dimensional materials with strong bandstructure anisotropy such as black phosphorus BP have been identified as attractive candidates for logic application due to their potential high carrier velocity and large density-of-states. However, perfectly aligning the source-to-drain axis with the desired crystal orientation remains an experimental challenge. In this paper, we use an advanced quantum transport approach from first-principle to shed light on the influence of orientation misalignments on the performance of BP-based field-effect transistors. Both $n$-and $p$-type configurations are investigated for six alignment angles, in the ballistic limit of transport and in the presence of electron-phonon and charged impurity scattering. It is found that up to deviations of $50^{\circ}$ from the optimal angle, the ON-state current only decreases by $30\%$. This behavior is explained by considering a single bandstructure parameter, the effective mass along transport direction.