GaN nanotip pyramids formed by anisotropic etching

Abstract

We experimentally demonstrate the formation of GaN nanotip pyramids by selective and anisotropic etching of N-polar GaN in KOH solution. For samples grown with adjacent Ga-and N-polar regions on the same wafer, the KOH solution was found to selectively etch only the N-polar surface while leaving the Ga-polar surface intact. An aggregation of hexagonal pyramids with well defined ͕10 1 1 ͖ facets and very sharp tips with diameters less than ϳ20 nm were formed. The density of the pyramids can be controlled by varying the KOH concentration, solution temperature or the etch duration. The GaN etching activation energy is estimated to be E a Ϸ0.587 eV. Dense GaN pyramids with sharp tips have applications in both electronic and photonic devices.

Dislocation- and crystallographic-dependent photoelectrochemical wet etching of gallium nitride

“…The hexagonal pyramid shape is consistent with other chemical etching studies of c-plane N-face GaN. 10 Indeed, the hexagonal inverted pyramid structure was observed as the V-defect structure observed in InGaN/GaN QW growth by MOCVD. 14 In contrast, no measurable etching was observed on the Ga face by comparison to the as-grown Ga face shown in Fig.…”

“…In addition, it is also interesting to explore the dramatically different chemical reactivities of the Ga and N face. 9,10 This work helps to elucidate such issues through etching of substrate materials formed by lateral epitaxial overgrowth ͑LEO͒ of nonpolar (112 0)a-GaN grown on an (11 02)r-plane sapphire substrate. The films used in these studies have two principal distinguishing features: ͑1͒ they were formed by metalorganic chemical vapor deposition ͑MOCVD͒ growth on a (11 02)r-plane sapphire substrate, producing a planar (112 0)a-GaN film and ͑2͒ essentially low dislocation density material was produced by lateral epitaxial overgrowth.…”

“…15 Lithographic patterning and MBE regrowth was used to define different lateral regions of Ga-and N-terminated GaN. 10 These regions also exhibited large difference in etch rate in a KOH solution. Further studies should be done to determine the reasons underlying the difference in etch rates between the Ga-face and N-face GaN.…”

Enhanced Cathodoluminescence of KOH-treated InGaN/GaN LEDs with Deep Nano-Hole Arrays

“…It reveals that, after the wet etching processes, the nanoholes are widened and tend to have an improved hexagonal symmetry. It is worth noting that the hole depth change is observed to be negligibly small, which is consistent with the facts that the GaN (0001) plane is chemically inert and that the GaN material has anisotropic etching properties, for which the etching rate is quite different for different crystal planes [19,20]. To observe inside the deep nano-hole arrays, we carry out cross-sectional SEM measurements using a dual-beam focused ion beam system (FIB-Nova600, Nova Lab).…”

Влияние параметров нитридизации и начальных ростовых условий на полярность эпитаксиальных слоев GaN, выращенных молекулярно-пучковой эпитаксией с плазменной активацией азота на подложках Si(111)

“…Несмотря на Ga-полярность, после травления можно наблюдать некоторые изменения морфологии поверхности в виде гексагональных ямок (рисунок, d). Первопричиной их появления может быть травление различного вида структурных дефектов, присутствующих в эпитаксиальном слое GaN: дислокаций [6], нанотрубок [7] или инверсионных доменов [8]. В то же время морфология бездефектных областей и толщина эпитаксиального слоя остались без изменений, что свидетельствует о Ga-полярности образца.…”