nanowires

We demonstrate a ballistic p−n junction in a three-dimensional Dirac semimetal (DSM) Cd₃As₂ nanowire with two recessed bottom gates. The device exhibits four different conductance regimes with gate voltages, confirming that device forms p−n junction. The conductance in the p−n junction regime decreases drastically when a magnetic field is applied perpendicular to the nanowire, which is due to the suppression of Klein tunneling. In this regime, the device shows quantum dot behavior. On the other hand, clear conductance plateaus are observed in the n−n regime likely owing to 1-D subbands of carriers at high magnetic fields. In other devices, we also observe Fabry-Perot interference in the p−n junctions, indicating that our devices are in the ballistic regime. Our experiment shows that the ambipolar tunability of DSM nanowires can enable the realization of quantum devices based on electron optics.