Development of a Photoelectrochemical Etch Process to Enable Heterogeneous Substrate Integration of Epitaxial III-Nitride Semiconductors

Report No. ARL-TR-8228
Authors: Vijay Parameshwaran; Roy B Chung; Stephen Kelley; Kimberley Olver; Blair C Connelly; Anand V Sampath; Meredith L Reed
Date/Pages: December 2017; 18 pages
Abstract: A process is developed to transfer epitaxially grown III-nitride films onto substrates more applicable to the desired application. The substrates for epitaxial growth of these films are limited to single-crystal sapphire, gallium nitride (GaN)-on-sapphire templates, or free-standing GaN. However, the desired end application requires a different substrate for optical, electrical, or thermal reasons. This process is applied for a semipolar (20-21) GaN lasing stack, grown on free-standing GaN, and designed for emission at a wavelength of 369 nm. A sacrificial indium gallium nitride (InGaN) layer, with an emission wavelength of 410 nm, is grown below the lasing stack. The stack is processed into 200 mesa structures to minimize the amount of undercut etch-rate limitations. The etching is performed in a 0.1-M potassium hydroxide solution under backside irradiation from a 405-nm laser such that only the sacrificial layer absorbs the incident radiation. The photogenerated holes induce a surface oxidation current, etching the sacrificial InGaN layer and promoting the release of the epitaxial lasing stack, which can then be automatically transferred to a previously bonded heterogeneous substrate.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2017