N-polar GaN p-n junction diodes with low ideality factors

TL;DR

This paper reports the fabrication of high-quality N-polar GaN p-n diodes with low ideality factors, high breakdown fields, and near-band edge electroluminescence, demonstrating performance comparable to Ga-polar devices.

Contribution

It presents the first realization of high-quality N-polar GaN p-n diodes with low ideality factors and high breakdown fields on single-crystal N-polar GaN substrates.

Findings

High on/off current ratio of 10^11 at 4 V

Ideality factor of 1.6 at room temperature

Reverse breakdown field of 2.4 MV/cm

Abstract

High-quality N-polar GaN p-n diodes are realized on single-crystal N-polar GaN bulk substrate by plasma-assisted molecular beam epitaxy. The room-temperature current-voltage characteristics reveal a high on/off current ratio of 10^11 at 4 V and an ideality factor of 1.6. As the temperature increases to 200 C, the apparent ideality factor gradually approaches 2. At such high temperatures, Shockley-Read-Hall recombination times of 0.32-0.46 ns are estimated. The measured electroluminescence spectrum is dominated by a strong near-band edge emission, while deep level and acceptor-related luminescence is greatly suppressed. A relatively high reverse breakdown field of 2.4 MV/cm without field-plates is achieved. This work indicates that the quality of N-polar GaN diodes is now approaching to that of their state-of-the-art Ga-polar counterparts.