The controlled fabrication of vertical, tapered, and high-aspect ratio GaN nanowires via a two-step top-down process consisting of an inductively coupled plasma reactive ion etch followed by a hot, 85% H₃PO₄ crystallographic wet etch is explored. The vertical nanowires are oriented in the direction and are bound by sidewalls comprising of semipolar planes which are at a 12 angle from the [0001] axis. High temperature H₃PO₄ etching between 60 C and 95 C result in smooth semipolar faceting with no visible micro-faceting, whereas a 50 C etch reveals a micro-faceted etch evolution. High-angle annular dark-field scanning transmission electron microscopy imaging confirms nanowire tip dimensions down to 8–12 nanometers. The activation energy associated with the etch process is 0.900.09 eV, which is consistent with a reaction-rate limited dissolution process. The exposure of the type planes is consistent with etching barrier index calculations. The field emission properties of the nanowires were investigated via a nanoprobe in a scanning electron microscope as well as by a vacuum field emission electron microscope. The measurements show a gap size dependent turn-on voltage, with a maximum current of 33 nA and turn-on field of 1.92 V nm⁻¹ for a 50 nm gap, and uniform emission across the array.

探索了通过两步自顶向下工艺控制制造垂直、锥形和高纵横比 GaN 纳米线，该工艺包括电感耦合等离子体反应离子蚀刻，然后是热的 85% H ₃ PO ₄晶体湿蚀刻。垂直纳米线在该方向上定向并且被侧壁约束，该侧壁包括与[0001]轴成12°角的半极性平面。高温 H ₃ PO ₄60°C 和 95°C 之间的蚀刻导致光滑的半极性刻面，没有可见的微刻面，而 50°C 刻蚀显示微刻面刻蚀演变。高角度环形暗场扫描透射电子显微镜成像证实纳米线尖端尺寸低至 8-12 纳米。与蚀刻过程相关的活化能为 0.900.09 eV，这与反应速率受限的溶解过程一致。字体平面的暴露与蚀刻阻挡指数计算一致。通过纳米探针在扫描电子显微镜以及真空场发射电子显微镜中研究了纳米线的场发射特性。测量结果显示间隙大小取决于开启电压，最大电流为 33 nA，开启场为 1.92 V nm^-1表示 50 nm 间隙，以及整个阵列的均匀发射。