Hierarchically porous GaN thin films fabricated using high fluence Ar ion implantation of epitaxial GaN on sapphire

Abstract

• We show the fabrication of hierarchical pores in GaN by means of Ar ion implantation. • This approach is free of the limitations of anodic etching of porous GaN. • There is no need for uniform current spreading to obtain uniform porosity. • The submission focuses on the material properties not on the implantation process. • We demonstrate different damage behavior for single and double ionized Ar. We show a method to fabricate porous gallium nitride (GaN) films without the need for wet chemical etching nor high donor concentrations in the starting material. The pores in epitaxial GaN films were formed using 200 keV Ar + ion implantation at fluences ranging from 2.5∙10 16 Ar + ∙cm −2 to 10 17 Ar + ∙cm −2 . The properties of the created nanostructures are discussed by means of complementary structural, optical and electrical studies. Electrochemical capacitance of the samples in an aqueous electrolyte is studied to deconvolute information about the surface area available after the implantation. Single and double ionized implantation is compared in the discussion and different damage in the two cases is shown. The results show information complementary to the current models of damage buildup in gallium nitride films upon high fluence irradiation as well as present a means of fabricating on-wafer porous areas for future GaN-based devices. The method overcomes the drawbacks of the commonly applied anodic etching: it does not require a high GaN donor concentrations nor difficult setups for achieving uniform etching. Furthermore, it can be applied locally using appropriate masking of the selected areas with a thick photoresist or other strippable inorganic ion stopping film.