N-polar GaN/AlN resonant tunneling diodes

Abstract

N-polar GaN/AlN resonant tunneling diodes are realized on single-crystal N-polar GaN bulk substrate by plasma-assisted molecular beam epitaxy growth. The room-temperature current-voltage characteristics reveal a negative differential conductance (NDC) region with a peak tunneling current of 6.8 ± 0.8 kA/cm 2 at a forward bias of ∼8 V. Under reverse bias, the polarizationinduced threshold voltage is measured at ∼ −4 V. These resonant and threshold voltages are well explained with the polarization field which is opposite to that of the metal-polar counterpart, confirming the N-polarity of the RTDs. When the device is biased in the NDC-region, electronic oscillations are generated in the external circuit, attesting to the robustness of the resonant tunneling phenomenon. In contrast to metal-polar RTDs, N-polar structures have the emitter on the top of the resonant tunneling cavity. As a consequence, this device architecture opens up the possibility of seamlessly interfacing-via resonant tunneling injection-a wide range of exotic materials with III-nitride semiconductors, providing a route to explore new device physics.