We report on the fabrication and characterization of fully vertical gallium nitride trench metal oxide semiconductor field effect transistors on native substrates with a metal-free gate first process and a chlorine-free trench etching method. Trenches were fabricated using sulfur hexafluoride and argon plasma etching in combination with alkaline wet etching posttreatment to create crystal oriented trenches along the a- and m-planes. Low pressure chemical vapor deposited silicon dioxide was used as gate dielectric with a poly-silicon gate contact. The metal-free gate structure was separated by a silicon dioxide passivation from any subsequent metal containing contact formation processing steps. The breakdown robustness of the gate structure was examined in the forward direction and no temperature dependence was observed up to 450 K. Fabricated trench MOSFETs showed only small hysteresis effects during transfer characterization but a positive threshold shift was observed. An inversion channel carrier field effect mobility of $\approx 10$ cm${}^2$/V s was extracted. The area specific on resistance was calculated to be 5.8 m$\mathrm{\Omega }$ cm${}^2$. Results for devices with differently oriented trenches were comparable and no significant performance difference was observed.

中文翻译：

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采用无金属栅极优先工艺制造的全垂直氮化镓沟槽MOSFET

我们用无金属栅极优先工艺和无氯沟槽刻蚀方法报告了本机衬底上的全垂直氮化镓沟槽金属氧化物半导体场效应晶体管的制造和特性。使用六氟化硫和氩等离子体蚀刻结合碱性湿蚀刻后处理来制造沟槽，以沿a平面和m平面生成晶体取向的沟槽。低压化学气相沉积二氧化硅用作具有多晶硅栅极触点的栅极电介质。通过二氧化硅钝化将无金属的栅极结构与任何后续的含金属的触点形成处理步骤分离。在正向方向上检查了栅极结构的击穿鲁棒性，直到450 K都没有观察到温度依赖性。制备的沟槽MOSFET在传输特性期间仅显示出很小的磁滞效应，但观察到正阈值漂移。反向信道载波场效应迁移率$\approx 10$ 厘米${}^{\mathrm{2个}}$/ V s被提取。计算得出的电阻抗面积为5.8 m$\mathrm{\Omega }$ 厘米${}^{\mathrm{2个}}$。具有不同取向的沟槽的器件的结果是可比较的，并且没有观察到明显的性能差异。