Porous Nitrides
Open Access Database for Porous Nitrides
At the Centre for Gallium Nitride, we carry out a large number of electrochemical etching experiments as part of our porous nitride research. To support the wider community, we are making these data openly available through a database linking etching conditions to the resulting porous morphologies, helping new groups enter the field more easily, reducing duplication of effort, and improving reproducibility across porous nitride research.
Processing Program for Porous Nitride DBRs
We have developed a processing program for the electrochemical etching of porous nitride distributed Bragg reflectors. This model simulates and provides insight into the formation of current-time traces (chronoamperometry) during the fabrication of porous GaN DBRs, as well as microstructural features of the resulting porous layers.
Porous Nitride Research at the Centre for Gallium Nitride
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.
Building on our work on distributed Bragg reflectors, we are now exploring a range of potential applications of porous nitrides. We spun out a company, Porotech, to exploit our porosification technology, and we are helping them to develop porous structures which allow strain relaxation in green, amber and red nitride light emitting diodes (LEDs). this should enable these longer wavelength devices to be more efficient, and is particularly important for microLEDs for display applications. We're also exploring porous nitrides for use in quantum light sources and sensors. Underpinning all this are our studies linking the fundamental structure and properties of porous nitride materials, exploiting expertise in microscopy and microanalysis. The porous nitrides also provide an exciting opportunity for the creation of composites of nitrides and other materials, via infiltration of a range of species into the pores, opening up potential for multifunction materials, combining the optoelectronic and piezoelectric properties of the nitrides with materials which exhibit ferromagnetism, ferroelectricity or other functionalities.
Porous Nitride Publications from the Group
B. Guilhabert, M. Toon, S. Ghosh, D. Jevtics, Z. Xia, M. J. Kappers, M. Dawson, R.A. Oliver, and M. Strain, "Co-integration of mesoporous GaN distributed Bragg reflectors and light-emitting diodes by transfer printing", Optics Letters, 2026, 51, 993-996. DOI: 10.1364/OL.584532
P. Sokolinksi, B. Thornley, Z. Xu, Y. Zhang, T. R. Harris-Lee, M. J. Kappers, R. A. Oliver, ‘A stochastic simulation of the dislocation-mediated etching of porous GaN distributed Bragg reflectors’, Journal of Applied Physics, 2026, 139, 205106. DOI: 10.1063/5.0324684
B. Thornley, Z. Xu, T. R. Harris-Lee, M. J. Kappers, P. Sokolinski, R. A. Oliver, ‘Optimization of porous GaN distributed Bragg reflectors via low-concentration oxalic acid electrochemical etching’, Journal of Applied Physics, 2026, 139, 185705. DOI: 10.1063/5.0321791
J. Zhang, B. Thornley, T. R. Harris-Lee, S. A. Dar, M. J. Kappers, R. A. Oliver, ‘The impact of dislocation-mediated etching on the structure of porous GaN’, Journal of Applied Physics, 2026, 139, 175702. DOI: 10.1063/5.0325215
B. Thornley, M. Sarkar, S. Ghosh, M. Frentrup, M. J. Kappers, T. R. Harris-Lee, R. A. Oliver, ‘A cascade model for the defect-driven etching of porous GaN distributed Bragg reflectors’, Acta Materiala, 2026, 308, 121957. DOI: 10.1016/j.actamat.2026.121957
T. R. Harris-Lee, Y. Zhang, B. Thornley, J. Zhang, M. J. Kappers, R. A. Oliver, ‘Analysis of in situ electrochemical characterization methods for porous GaN distributed Bragg reflectors’, Journal of Applied Physics, 2026, 139, 135702. DOI: 10.1063/5.0325374
T. R. Harris-Lee, B. Thornley, J. Zhang, M. J. Kappers, R. A. Oliver, ‘Porous GaN: Anion-Specific Electrochemical Etching Mechanisms and Morphological Control’, ACS Applied Materials and Interfaces, 2025, 17, 64931-64941. DOI: 10.1021/acsami.5c18520
S. Ghosh, M. Sarkar, M. Frentrup, M.J. Kappers, and R.A. Oliver, "Microstructure and reflectance of porous GaN distributed Bragg reflectors on silicon substrates", J. Appl. Phys., 2024, 136, 043105. DOI: 10.1063/5.0216672
X. Bai, S.M. Fairclough, L. Dai, M. Sarkar, P.H. Griffin, A. Gundimeda, Y. Sun, N.C. Greenham, M.I. Dar, R.A. Oliver, and R.H. Friend, "Enhanced Excitonic Nature of MAPbBr3 Nanocrystals in Nanoporous GaN", Adv. Optical Mater., 2024, 12, 2400221. DOI: 10.1002/adom.202400221
Y. Ji, M. Frentrup, S. M. Fairclough, Y. Liu, T. Zhu, and R. A. Oliver, "Microscopy studies of InGaN MQWs overgrown on porosified InGaN superlattice pseudo-substrates", Semicond. Sci. Technol., 2024, 39, 085001. DOI: 10.1088/1361-6641/ad575b
M. Sarkar, F. Adams, S. A. Dar, J. Penn, Y. Ji, A. Gundimeda, T. Zhu, C. Liu, H. Hirshy, F. C -P Massabuau, T. O’Hanlon, M. J. Kappers, S. Ghosh, G. Kusch, and R. A. Oliver, "Sub-surface Imaging of Porous GaN Distributed Bragg Reflectors via Backscattered Electrons", Microsc. Microanal., 2024, 00, 1–18. DOI: 10.1093/mam/ozae028
Y. Ji, M. Frentrup, X. Zhang, J. Pongrácz, S. M. Fairclough, Y. Liu, T. Zhu, and R. A. Oliver, "Porous pseudo-substrates for InGaN quantum well growth: Morphology, structure, and strain relaxation", J. Appl. Phys., 2023, 134, 145102. DOI: 10.1063/5.0165066
R. A. Oliver, "LED applications of electrochemical sub-surface porosification of nitrides", Light-Emitting Devices, Materials, and Applications XXVII conference at SPIE OPTO, 2023. DOI: 10.1117/12.2668387
Y. Grishchenko, J. Dawson, S. Ghosh, A. Gundimeda, B. F. Spiridon, N. L. Raveendran, R. A. Oliver, S. Kar-Narayan, and Y. Calahorra, "Magnetic properties of nickel electrodeposited on porous GaN substrates with infiltrated and laminated connectivity", J. Magn. Magn. Mater., 2023, 580, 170877. DOI: 10.1016/j.jmmm.2023.170877
Y. Calahorra, J. Dawson, Y. Grishchenko, S. Ghosh, A. Gundimeda, B. F. Spiridon, R. A. Oliver, and S. Kar-Narayan, "Magnetization and magnetoresistance of infiltrated and coated porous-GaN/nickel composites", arXiv preprint 2021; arXiv: 2102.02904
P. H. Griffin and R. A. Oliver, "Porous nitride semiconductors reviewed", J. Phys. D: Appl. Phys.53, 383002 (2020); DOI: 10.1088/1361-6463/ab9570
P. H. Griffin, K.M. Patel, T. Zhu, R. M. Langford, V. S. Kamboj, D. A. Ritchie, and R. A. Oliver, "The relationship between the three-dimensional structure of porous GaN distributed Bragg reflectors and their birefringence", J. Appl. Phys.127 (19), 193101 (2020); DOI: 10.1063/5.0005770
F. C.-P. Massabuau, P. H. Griffin, H. P. Springbett, Y. Liu, R. V. Kumar, T. Zhu, and R. A. Oliver, "Dislocations as channels for the fabrication of sub-surface porous GaN by electrochemical etching", APL Materials8 (3), 031115 (2020); DOI: 10.1063/1.5142491
P. H. Griffin, M. Frentrup, T. Zhu, M. E. Vickers, and R. A. Oliver, "Structural characterization of porous GaN distributed Bragg reflectors using x-ray diffraction", J. Appl. Phys.126 (21), 213109 (2019); DOI:10.1063/1.5134143
J. C. Jarman, T. Zhu, P. H. Griffin, and R. A. Oliver, "Light-output enhancement of InGaN light emitting diodes regrown on nanoporous distributed Bragg reflector substrates", Jpn. J. Appl. Phys.58, SCCC14 (2019); DOI: https://doi.org/10.7567/1347-4065/ab0cfd
K.T.P. Lim, C. Deakin, B. Ding, X. Bai, P. Griffin, T. Zhu, R. Oliver, and D. Credgington, "Encapsulation of methylammonium lead bromide perovskite in nanoporous GaN", APL Materials7, 021107 (2019); DOI: 10.1063/1.5083037
H. P. Springbett, K. Gao, J. Jarman, T. Zhu, M. Holmes, Y. Arakawa, and R. A. Oliver, "Improvement of single photon emission from InGaN QDs embedded in porous micropillars", Appl. Phys. Lett.113, 101107 (2018); DOI: 10.1063/1.5045843
P. Griffin, T. Zhu, and R. Oliver, “Porous AlGaN-Based Ultraviolet Distributed Bragg Reflectors”, Materials11, 1487 (2018); DOI: 10.3390/ma11091487
B. F. Spiridon, P. H. Griffin, J. C. Jarman, Y. Liu, T. Zhu, A. De Luca, R. A. Oliver, and F. Udrea,"On-Chip Thermal Insulation Using Porous GaN", Proceedings2, 776 (2018); DOI:10.3390/proceedings2130776
Zhu, T., Liu, Y., Ding, T., Fu, W. Y., Jarman, J., Ren, C. X., Kumar, R. V., Oliver, R. A., “Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosification”, Scientific Reports, 7, 45344, (2017), DOI: 10.1038/srep45344