• Zhu, Tongtong
• Kumar, R. Vasant
• Liu, Yingjun
• Springbett, Helen P.
• Griffin, Peter H.
• Oliver, Rachel A.
• Massabuau, Fcp

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.

Topics

• porous
• impedance spectroscopy
• surface
• semiconductor
• nitride
• dislocation
• etching
• electron microscopy
• porosity