  The integration of two-dimensional materials such as transition metal
dichalcogenides with bulk semiconductors offer interesting opportunities for
2D/3D heterojunction-based novel device structures without any constraints of
lattice matching. By exploiting the favorable band alignment at the GaN/MoS2
heterojunction, an Esaki interband tunnel diode is demonstrated by transferring
large area, Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current
density of 446 A/cm2 with repeatable room temperature negative differential
resistance, peak to valley current ratio of 1.2, and minimal hysteresis was
measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of
1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The
GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk
semiconductor, and the electrostatics at the 2D/3D interface was found to be
crucial in explaining the experimentally observed device characteristics.
