In SiN/AlGaN/GaN heterostructures, the evaluation of interface charges at the SiN/AlGaN and AlGaN/GaN interfaces is crucial since they both rule the formation of the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. In this paper, we conducted a thorough analysis of the gate-to-channel capacitance C_GC(V_G) and of the drain current I_D(V_G) over a gate voltage V_G range enabling the depletion of the 2DEG and the formation of the electron channel at the SiN/AlGaN interface. This work includes the establishment of analytical equations for $V_{TH1}$ (formation of the 2DEG) and $V_{TH2}$ (formation of the electron channel at the SiN/AlGaN interface) as a function of interface charges and of the p-doping below the 2DEG. The inclusion of the p-doped layer below the 2DEG and the use we made of $V_{TH2}$ have not been reported in previous studies. Our analysis allows a reliable estimate of the interface charges at the Al_xGa_1−xN/GaN and SiN/Al_xGa_1−xN interfaces for various Al concentrations $x$ as well as to demonstrate that the polarization charge at the SiN/Al_xGa_1−xN interface is compensated, which confirms previous findings. Moreover, this compensation is found to be induced by the AlGaN layer rather than the SiN layer.

中文翻译：

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通过分析栅沟道电容和漏电流行为研究 SiN/AlxGa1−xN/GaN 异质结构中的界面电荷

在 SiN/AlGaN/GaN 异质结构中，SiN/AlGaN 和 AlGaN/GaN 界面的界面电荷评估至关重要，因为它们都决定了 AlGaN/GaN 界面处二维电子气 (2DEG) 的形成。在本文中，我们对栅极-沟道电容C _GC ( V _G ) 和漏极电流I _D ( V _G ) 在栅极电压V _G范围内进行了彻底分析，从而使 2DEG 耗尽并形成SiN/AlGaN 界面处的电子通道。这项工作包括建立解析方程${伏}_{吨H1}$ （2DEG的形成）和 ${伏}_{吨H2}$（在 SiN/AlGaN 界面形成电子通道）作为界面电荷和 2DEG 以下 p 掺杂的函数。在 2DEG 下方包含 p 掺杂层以及我们使用的${伏}_{吨H2}$在以往的研究中未见报道。我们的分析允许对不同 Al 浓度的 Al _x Ga _1-x N/GaN 和 SiN/Al _x Ga _1-x N 界面处的界面电荷进行可靠估计$X$以及证明 SiN/Al _x Ga _1-x N 界面处的极化电荷得到补偿，这证实了先前的发现。此外，发现这种补偿是由 AlGaN 层而不是 SiN 层引起的。