In this work, we observe the distinct V_TH characteristics in the Au-free gate-first processing p-GaN/AlGaN/GaN HEMTs with two commonly used passivation layers, i.e., SiN and SiO₂. The lower incorporated H was found in the p-GaN/AlGaN/GaN heterostructure with higher activation anneal temperature (i.e., 700 °C). Furthermore, Photoluminescence (PL) spectrum demonstrates a higher blue luminescence (BL) intensity after higher annealing treatment. The X-ray photoelectron spectroscopy (XPS) spectrum near valence band edge depicts a similar valence band maximum (VBM) characteristic, by means no impact on p-GaN surface bending by using distinct thermal treatment. The device with SiN shows a depletion-mode (D-mode) characteristic (V_TH ~ -5 V) whereas the device with SiO₂ passivation exhibits an enhancement-mode (E-mode) characteristic (V_TH ~ +0.7 V). Moreover, Transmission Line Model (TLM) devices are fabricated to investigate the effects of the passivation on two-dimensional electron gas (2DEG) in p-GaN/AlGaN/GaN stack. The results indicate that a low R_sh is obtained while passivating device surface with SiN layer, suggesting that 2DEG is present, which is most probably due to an unfunctional p-GaN layer. The secondary ion mass spectrometry (SIMS) results indicate a high hydrogen intensity in the p-GaN/AlGaN/GaN stack with a SiN passivation layer. Thus, the p-GaN deactivation process that correlates to the formation of complex MgH after SiN passivation is proposed to explain the D-mode characteristic in the device with a SiN passivation layer.

在这项工作中，我们观察到在具有两个常用钝化层（即SiN和SiO _2）的无金的先栅处理p-GaN / AlGaN / GaN HEMT中的独特V _TH特性。在激活退火温度较高（即700°C）的p-GaN / AlGaN / GaN异质结构中发现了较低的掺入H。此外，光致发光（PL）光谱显示出较高的退火处理后更高的蓝色发光（BL）强度。价带边缘附近的X射线光电子能谱（XPS）光谱显示出相似的价带最大值（VBM）特性，通过使用不同的热处理不会对p-GaN表面弯曲产生影响。具有SiN的器件显示出耗尽模式（D模式）特性（V _TH 〜-5V）而具有的SiO设备₂钝化表现出增强模式（ê -mode）特性（V _TH  〜0.7 V）。此外，制造了传输线模型（TLM）器件以研究钝化对p-GaN / AlGaN / GaN叠层中的二维电子气（2DEG）的影响。结果表明，在用SiN层钝化器件表面时获得了较低的R _sh，这表明存在2DEG，这很可能是由于p-GaN层功能失调所致。二次离子质谱（SIMS）结果表明，具有SiN钝化层的p-GaN / AlGaN / GaN叠层中的氢强度很高。因此，与复杂Mg的形成相关的p-GaN失活过程提出了SiN钝化后的H来解释具有SiN钝化层的器件中的D模式特性。