Degradation of GaN-on-GaN vertical diodes submitted to high current stress
Degradation of GaN-on-GaN vertical diodes submitted to high current stress
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DOI：
10.1016/j.microrel.2018.06.041
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发表时间：
2018-09-01
影响因子：
1.6
通讯作者：
Zanoni, E.
中科院分区：
文献类型：
--
作者：
Fabris, E.;Meneghini, M.;Zanoni, E.
GaN-on-GaN垂直器件由于具有高电流密度、低导通电阻和高击穿电压等优点，在电力电子领域有着广泛的应用前景。到目前为止，只有少数论文GaN上GaN垂直器件的可靠性已在文献中发表。本文研究了GaN上GaN pn二极管在高电流密度下受到应力时的退化。通过电特性和电致发光（EL）测量进行了研究。我们证明：（i）当在高电流密度下经受应力时，器件显示出电特性的显著变化：导通电阻/导通电压的增加、产生/复合分量的增加、分流路径的产生。(ii)导通电阻的增加与二极管发射的EL信号的减小密切相关。(iii)降解动力学具有对时间的平方根依赖性，指示扩散过程。考虑到应力诱导氢从高p型掺杂表面向pn结扩散，解释了结果。由于MgH键的产生，这导致空穴浓度降低，并且导致较低的空穴注入。因此，导通电阻增加，而EL信号显示出相关的减少。
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.