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Porous Nitrides

PorousStructure
Schematic of the set-up used to electrochemically etch a layered GaN structure to produce a porous DBR, as shown in the SEM image, right.

Using a simple electrochemical technique we can create nanoscale porosity in nitride structures, which can be used to change the material's properties in a number of ways. We have demonstrated highly reflective Distributed Bragg Reflectors (DBRs) by creating layers of porous and non-porous material. The etch responds differently to the material depending on its doping density, so a high degree of control is possible through the material growth of the structure to control the doping density of each layer. What's more, the parameters of the etch process can also be used to control the morphology of the pores and which layers etch.

PorousColourCropped2
Photograph of porous DBRs, showing how the colour can be tuned across the visible range. This demonstrates only some of the large variation in control we have over the structure using this method.

 

Porosification presents a powerful method for changing the behaviour of a material and through this method we can achieve broad control over the structure. We are exploring how it can be used in a variety of novel photonic devices.

Key researchers working on this area: Tongtong Zhu, Peter Griffin, John Jarman and Rachel Oliver.