In this article, we present an extensive investigation of the time-dependent drain breakdown occurring in GaN-on-Si power HEMTs with p-GaN gate under long-term OFF-state stress. In particular, the time-dependent breakdown induced by high-temperature-reverse-bias stress is investigated as a function of different process and structural variations. Main results demonstrate that, by varying the gate-to-drain distance ( $\text{L}_{\mathrm{ GD}}$ ) and the field plates configuration, the physical location of failure changes as well. If $\text{L}_{\mathrm{ GD}}$ is relatively short ( $3~\mu \text{m}$ ), the time-dependent breakdown occurs through the GaN channel layer between drain and source. In this case, a thinner GaN layer significantly improves the device robustness to long-term OFF-state stress. If $\text{L}_{\mathrm{ GD}}$ is relatively long ( $\ge 4 ~\mu \text{m}$ ), the failure occurs between the two-dimensional electron gas (2DEG) and the source field plates. In this second case, the GaN layer thickness and $\text{L}_{\mathrm{ GD}}$ have no significant impact on the time-dependent breakdown, whereas the field plate lengths can be optimized to reduce the area exposed to high electric fields, hence limiting the probability of failure. Finally, the role of the AlGaN barrier layer has been analyzed as well. If $\text{L}_{\mathrm{ GD}} = 3 ~\mu \text{m}$ , a thinner AlGaN layer is preferred, whereas if $\text{L}_{\mathrm{ GD}} \ge 4 ~\mu \text{m}$ , a thicker layer with lower aluminum content gives rise to longer time to breakdown under OFF-State stress.

中文翻译：

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结构和工艺变化对p-GaN功率HEMT随时间变化的截止态击穿的影响

在本文中，我们对长期处于关态应力下具有p-GaN栅极的GaN-on-Si功率HEMT中发生的随时间变化的漏极击穿进行了广泛的研究。尤其是，研究了高温反向偏应力引起的随时间变化的击穿现象，该过程是不同过程和结构变化的函数。主要结果表明，通过改变栅极到漏极的距离（ $ \ text {L} _ {\ mathrm {GD}} $ ）和场板配置，故障的物理位置也会发生变化。如果 $ \ text {L} _ {\ mathrm {GD}} $ 相对较短（ $ 3〜\ mu \ text {m} $ ），时间依赖性击穿发生在漏极和源极之间的GaN沟道层上。在这种情况下，较薄的GaN层可显着提高器件对长期处于关态应力的鲁棒性。如果 $ \ text {L} _ {\ mathrm {GD}} $ 相对较长（ $ \ ge 4〜\ mu \ text {m} $ ），故障发生在二维电子气（2DEG）和源场板之间。在第二种情况下，GaN层的厚度和 $ \ text {L} _ {\ mathrm {GD}} $ 对时间相关的击穿没有显着影响，而可以优化场板的长度以减少暴露于高电场的面积，从而限制了故障的可能性。最后，还分析了AlGaN势垒层的作用。如果 $ \ text {L} _ {\ mathrm {GD}} = 3〜\ mu \ text {m} $ ，较薄的AlGaN层是优选的，而如果 $ \ text {L} _ {\ mathrm {GD}} \ ge 4〜\ mu \ text {m} $ ，具有较低铝含量的较厚层在断态应力下会导致更长的击穿时间。