N-polar GaN/AlN resonant tunneling diodes

TL;DR

This paper reports the fabrication and characterization of N-polar GaN/AlN resonant tunneling diodes demonstrating negative differential conductance and electronic oscillations, with unique device architecture enabling novel material integration.

Contribution

It introduces N-polar GaN/AlN RTDs with a new device architecture that allows seamless interfacing with exotic materials via resonant tunneling injection.

Findings

Peak tunneling current of 6.8 kA/cm² at ~8 V

Observation of electronic oscillations in the NDC region

Polarization-induced threshold voltage at -4 V

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$\pm$ 0.8 kA/cm$^2$ at a forward bias of ~8 V. Under reverse bias, the polarization-induced 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.