Abstract Surface etching methods were investigated for the removal of residues of chemical reagents and contaminants from polar (Ga- and N-plane), semipolar (r-plane) and nonpolar (a- and m-plane) freestanding GaN surfaces. Ga-, N-, r- and m-plane were etched in H3PO4, NaOH and (NH4)2S solutions. A-plane was treated in the solution of 10 wt% KOH in ethylene glycol (EG) at 80 °C. Different surface morphology were obtained and were characterized with atomic force microscope. The typical characteristics for the surface morphologies and interfacial angles in each etched GaN plane may help identify the type of crystal plane conveniently. Ga-polar GaN shows a clear and uniform step structure on surfaces. N-plane presented a step structure with tooth-like terraces. The ( 2 0 2 ¯ 1 ) r-plane, m-plane and a-plane show stripe-like structures, while the ( 2 0 2 ¯ 1 ¯ ) r-plane is stable and hard to be etched to exhibit step structures. The m-plane facets on a-plane surface caused by the etching method was found and discussed.

中文翻译：

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化学蚀刻后极性、半极性和非极性独立 GaN 的表面形貌

摘要 研究了用于从极性（Ga 和 N 面）、半极性（r 面）和非极性（a 面和 m 面）独立 GaN 表面去除化学试剂和污染物残留物的表面蚀刻方法。Ga-、N-、r-和m-平面在H3PO4、NaOH和(NH4)2S溶液中蚀刻。在 80 °C 下，在 10 wt% KOH 的乙二醇 (EG) 溶液中处理 A 平面。获得了不同的表面形态，并用原子力显微镜表征。每个蚀刻的 GaN 平面的表面形貌和界面角的典型特征可以帮助方便地识别晶面类型。Ga 极性 GaN 在表面上显示出清晰且均匀的阶梯结构。N面呈带齿状阶地的阶梯状结构。( 2 0 2 ¯ 1 ) r 面、m 面和 a 面呈现条纹状结构，而 ( 2 0 2 ¯ 1 ¯ ) r 面是稳定的，很难被蚀刻以表现出阶梯结构。发现并讨论了由蚀刻方法引起的a平面表面上的m平面小平面。