III-Nitride based light-emitting diodes (LEDs) are highly energy-efficient and their widespread usage in lighting can induce significant worldwide electricity savings. The effective way of getting efficient white and color-tunable lighting is by a combination of red, blue and green LEDs. At present, the efficiency of green-wavelength LEDs is only about half of that of red- and blue-wavelength LEDs. This is known as the ‘green gap’ problem. It relates the low efficiency of such devices to strong internal electric polarization fields across the quantum wells (QWs) of the commonly used wurtzite c-orientation. Also, achieving green emission in wurtzite GaN requires more Indium rich quantum wells. But, instilling more indium into QWs compromises the material quality with high point defect densities. Cubic zincblende GaN has the potential to bridge the ‘green gap’ due to the theoretical absence of internal electric fields. Also, having a smaller bandgap in cubic zincblende GaN compared to the wurtzite phase requires less indium in InGaN quantum wells to reach the green wavelength region.
The aim of my PhD project at the Cambridge Centre for Gallium Nitride is to develop zincblende GaN materials, which include nucleation layers, InGaN/GaN multi-quantum wells for the growth of efficient green LEDs. One of the key aspects is to understand how defects and wurtzite inclusions are formed and to develop strategies to suppress their formation. This will involve characterising the material structure and correlating it with the device properties by a variety of techniques such as Atomic force microscopy, Electron microscopy and X-ray diffraction.
A full list of my publications can be found on my Google scholar profile and ResearchGate.
Further details can also be found on my LinkedIn.
