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Cubic Nitride LEDs

band tBlue light-emitting diodes for white lighting are based on wurtzite InGaN heteroepitaxial systems, however difficulties in achieving green emission by increasing the indium content results in reduced quantum efficiencies due to higher defect densities, and the internal electric field present in wurtzite nitrides limits efficient carrier recombination.  Cubic nitride films do not have this electric field, are suitable for silicon (001) electronics integration, and have a narrower bandgap and can have a higher p-type conductivity than hexagonal wurtzite GaN, resulting in the need for less indium and magnesium in the active and p-type layers respectively.

However, the cubic nitride structure is metastable and growth has until recently been shown to form mixed-phase films with high defect densities and poor emission properties. 

cubicwaferlargeIn collaboration with Anvil Semiconductors, we have successfully grown cubic GaN on 3C-SiC substrates, and with funding through a new Innovate UK grant in partnership with Anvil and Plessey, we plan to grow prototype green LEDs and related devices, with processing, packaging and steps towards commercialisation.