期刊
MICROELECTRONICS RELIABILITY
卷 88-90, 期 -, 页码 568-571出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.microrel.2018.06.041
关键词
Wide band gap semiconductors; Gallium nitride; pn junction; Vertical diodes; Bulk GaN substrates; Diffusion; Hydrogen; Degradation
资金
- Novel vertical GaN-devices for next generation power conversion, NoveGaN (University of Padova), through the STARS CoG
GaN-on-GaN vertical devices are expected to find wide application in power electronics, thanks to the high current densities, the low on-resistance and the high breakdown voltage. So far, only few papers on the reliability of GaN-on-GaN vertical devices have been published in the literature. This paper investigates the degradation of GaN-on-GaN pn diodes submitted to stress at high current density. The study was carried out by means of electrical characterization and electroluminescence (EL) measurements. We demonstrate that: (i) when submitted to stress at high current density, the devices show significant changes in the electrical characteristics: an increase in on-resistance/turn-on voltage, an increase in the generation/recombination components, the creation of shunt-paths. (ii) the increase in on-resistance is strongly correlated to the decrease in the EL signal emitted by the diodes. (iii) the degradation kinetics have a square-root dependence on time, indicative of a diffusion process. The results are interpreted by considering that stress induces a diffusion of hydrogen from the highly-p-type doped surface towards the pn junction. This results in a decrease in hole concentration, due to the creation of MgH bonds, and in a lower hole injection. As a consequence, on-resistance increases while EL signal shows a correlated decrease.
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