通过比较反向偏压下AlGaN/GaN异质结肖特基势垒二极管(SBD)和GaN SBD的电流特性、电场分布和光发射位置, 研究了GaN基SBD的漏电流传输与退化机制。结果表明, AlGaN/GaN SBD退化前后漏电流均由Frenkel-Poole(FP)发射机制主导, 而GaN SBD低场下为FP发射电流, 高场下则为Fowler-Nordheim(FN)隧穿电流。电场模拟和光发射测试结果表明, 引起退化的主要原因是高电场, 由于结构不同, 两种SBD的退化机制和退化位置并不相同。根据实验结果, 提出了一种高场FN隧穿退化模型, 该模型强调应力后三角势垒变薄导致FN隧穿增强是GaN SBD退化的内在机制。

In this paper, the transmission and degradation mechanisms of leakage current in GaN-based Schottky barrier diode (SBD) were investigated by comparing the current characteristics, electric field distribution and optical emission positions of AlGaN/GaN heterojunction SBDs with that of GaN SBD under reverse bias. The results indicate that the leakage current of AlGaN/GaN SBD before and after degradation is dominated by the Frenkel-Poole (FP) emission mechanism, while that of GaN SBD is composed of the low-field FP emission current and high-field Fowler-Nordheim (FN) tunneling current. The results of electric field simulation and light emission test indicate that the degradation is mainly induced by high electric field, the degradation positions and mechanisms of the two kinds of SBD are different due to their different structures. Based on the experimental results, a degradation model associating with high field FN tunneling is developed, which emphasizes that the enhanced FN tunneling process due to a thinner triangular barrier after stress is the inherent mechanism of degradation in GaN SBD.