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Cambridge Centre for Gallium Nitride


The work by our PhD student Maruf Sarkar has been chosen as cover image for the latest volume of the Microscopy and Microanalysis journal.

The sub-surface image of a porous GaN distributed Bragg reflector (DBR) has been captured by backscattered electron scanning electron microscopy (BSE-SEM). The DBR is fabricated by epitaxy of undoped and highly Si-doped GaN pairs followed by doping-selective electrochemical etch-ing. Here, a Zeiss GeminiSEM 300 operating at a 20 keV landing energy enables non-destructive characterization. By imaging through the 45 nm GaN cap, BSE-SEM reveals the morphology of the first porous layer, 45 nm to 108 nm sub-surface. The contrast relates to material density: high-density (white, GaN), medium-density (grey, sub-surface pores), and low-density (black, open volumes at threading dislocation cores). In such DBRs, BSE-SEM images the same branching pores and Voronoi-like domains as scanning transmission electron microscopy. For further details see the manuscript by Maruf Sarkar et al on the journal website (link).


We conduct world leading research into nitride based III-V semiconductors: material quality, characterisation and device development.

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