Department of Materials Science and Metallurgy
University of Cambridge
27 Charles Babbage Road
Cambridge CB3 0FS
My PhD project is broadly on the growth of GaN on novel Si-based substrates. I am currently involved in two projects.
Growth of GaN on Si substrates using rare-earth oxide buffer layers
Traditionally GaN has been grown on sapphire substrates, however the cost and size of sapphire wafers limits further development of this route. Recently there has been a lot of interest in producing GaN power electronic devices on Si substrates, due to lower cost, availability of larger (6 or 8 inch) wafers, and CMOS compatibility of Si wafers. However growing GaN on Si is not easy, due to lattice mismatch and difference in thermal expansion coefficients between the two materials. Rare-earth oxides have the potential to act as effective buffers between GaN and the Si substrate. Currently I am using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and 3-omega thermal conductivity technique to investigate the properties of the rare-earth oxide substrates. GaN and GaN devices will be investigated in the near future.
Growth of cubic GaN on 3C-SiC/Si substrates
Cubic GaN has advantages over traditional hexagonal GaN, such as absence of strong internal fields and smaller band gap, which are both beneficial to the production of efficient green-wavelength LEDs. Challenges arise during growth as cubic GaN is a metastable phase, and growth of hexagonal GaN is thermodynamically preferred. The aim of the project is to grow high quality cubic GaN on 3C-SiC/Si substrates. To achieve this aim, I am currently investigating the factors that affect growth and trying to understand the growth mechanism, through techniques such as AFM and X-ray diffraction (XRD).