Dislocations as channels for the fabrication of sub-surface porous GaN by electrochemical etching

Massabuau, Fabien C.-P. and Griffin, Peter H. and Springbett, Helen P. and Liu, Yingjun and Kumar, R. Vasant and Zhu, Tongtong and Oliver, Rachel A. (2020) Dislocations as channels for the fabrication of sub-surface porous GaN by electrochemical etching. APL Materials, 8 (3). 031115. ISSN 2166-532X

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    Abstract

    Porosification of nitride semiconductors provides a new paradigm for advanced engineering of the properties of optoelectronic materials. Electrochemical etching creates porosity in doped layers whilst leaving undoped layers undamaged, allowing the realisation of complex three-dimensional porous nanostructures, potentially offering a wide range of functionalities, such as in distributed Bragg reflectors. Porous/non-porous multilayers can be formed by etching whole, as-grown wafers uniformly in one simple process, without any additional processing steps. The etch penetrates from the top down, through the undoped layers, leaving them almost untouched. Here, atomic-resolution electron microscopy is used to show that the etchant accesses the doped layers via nanometre-scale channels that form at dislocation cores and transport the etchant and etch products to and from the doped layer respectively. Results on AlGaN and non-polar GaN multilayers indicate the same mechanism is operating, suggesting this approach may be applicable in a range of materials.