Reliability Investigations of AlGaN/GaN HEMTs Based on On-State Electroluminescence Characterization
Reliability Investigations of AlGaN/GaN HEMTs Based on On-State Electroluminescence Characterization
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DOI：
10.1109/tdmr.2014.2360891
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发表时间：
2015-03
影响因子：
2
通讯作者：
C. Zeng;Yuansheng Wang;X. Liao;Ruguan Li;Yiqiang Chen;P. Lai;Yun Huang;Y. En
中科院分区：
文献类型：
--
作者：
C. Zeng;Yuansheng Wang;X. Liao;Ruguan Li;Yiqiang Chen;P. Lai;Yun Huang;Y. En
本文研究了不同ON-state偏置条件下新鲜gan基hemt的ON-state电致发光（EL）特性。结果表明：1)具有较高VDS （VDS bbb10 V）的gan基hemt的on态EL强度随栅极电压的增加而单调增加；2)应力测试前，导通态电致发光强度沿栅和器件的分布是均匀的。基于on -state EL表征、电性测量和失效分析，分析了器件在高温工作应力下的降解过程和机理。它演示了以下内容。首先，经过阶梯HTO （S-HTO）应力测试后，器件的ON-state EL沿某一指的分布不再均匀，这表明退化与该指有关。这一假设在栅极金属和SiN钝化层脱制后的SEM观察中得到了证实。其次，确定了在S-HTO应力下引起突变降解的AlGaN/GaN hemt的新降解机制，并将其与栅金属下的突发性、局部性和锯齿状裂纹有关。第三，在长期HTO （LT-HTO）压力测试中没有出现突然退化。但是，经过LT-HTO应力测试后，器件内指的ON-state EL强度下降幅度大于外指，说明由于器件内部区域自热引起的温度较高，内指的降解速度要快于外指。最后，在LT-HTO应力测试中，逐渐退化归因于沿整个浇口边缘的漏侧逐渐形成结构损伤，这一点通过SEM观察得到了证实。
In this paper, we investigated ON-state electroluminescence (EL) characteristics in fresh GaN-based HEMTs under different ON-state bias conditions. It demonstrated that: 1) the intensity of the ON-state EL emitted by the GaN-based HEMTs with relatively high VDS (VDS > 10 V) monotonically increased as the gate voltage increased; and 2) the distribution of the intensity of the ON-state EL was uniform along the gate and across the device before stress tests. The degradation process and mechanisms of the devices in the high temperature operation (HTO) stress were also analyzed based on the ON-state EL characterization, the electrical measurement, and failure analysis. It demonstrated the following. First, the ON-state EL distribution of the device after step HTO (S-HTO) stress tests was no longer uniform along one of the fingers, which indicated that the degradation was related to this finger. This hypothesis was confirmed by the SEM observation after the deprocess of the gate metal and the SiN passivation layer. Second, a new degradation mechanism of AlGaN/GaN HEMTs that caused the abrupt degradation in the S-HTO stress was identified and related to the emergent, localized, and jagged crack under the gate metal. Third, there was no abrupt degradation in the long-term HTO (LT-HTO) stress test. However, the ON-state EL intensity of the inner fingers in the device after the LT-HTO stress test decreased more than that of the outer fingers, which meant that the degradation of the inner fingers was faster than that of the outer fingers as a result of the higher temperature caused by self-heating in the inner region of the device. Finally, the gradual degradation in the LT-HTO stress test was ascribed to the gradual formation of structural damage along the drain side of the whole gate edge, which was confirmed by the SEM observation.