The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of “Al” from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of “Pt” top Ohmic contacts. The application of a top “Pt” contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C.

中文翻译：

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温度对 III 族氮化物 HEMT 磁场传感器稳定性和性能的影响


该研究旨在调查大气条件下限制非表面钝化 Al0.34Ga0.66N/GaN 霍尔效应传感器（包括触点）的温度稳定性和性能的潜在物理原理。通过分析 Al0.34Ga0.66N/GaN 霍尔传感器异质结构的微观结构演变获得的结果与霍尔效应传感器的电气性能相关。高分辨率 X 射线光电子能谱研究揭示了 GaN 盖层中的表面氧化特征，以及 AlGaN 势垒层中“Al”的轻微外扩散。为了防止在欧姆接触处形成凹凸不平的表面形态，我们研究了“Pt”顶部欧姆接触的影响。顶部“Pt”接触叠层的应用产生了光滑的欧姆接触表面，并证明金基欧姆接触中凹凸不平的表面形态是由于快速热退火过程中铝-金粘性合金的形成所致。在热老化的早期阶段，接触电阻率的小幅下降随着随后在 200 °C 下经过最初 550 小时的热老化而稳定下来。结果是，即使没有表面钝化，Al0.34Ga0.66N/GaN 霍尔效应传感器也能对施加的磁场表现出稳定的响应，在大气条件下 200 °C 的热老化 2800 小时后没有明显退化的迹象。在没有表面钝化的霍尔传感器中观察到的这种稳定性可归因于老化早期阶段盖层的自强表面氧化，盖层在随后的 200° 长时间热老化期间充当器件的保护层C。