The III-Nitride Materials and Devices group started with the arrival of Peter Parbrook, who was appointed to a Stokes Professorship at Tyndall, in association with the Department of Electronic and Electrical Engineering at University College Cork. The position is sponsored for the first five years by Science Foundation Ireland. Professor Parbrook arrived in April 2009 and has over the months built up a team of dedicated scientists; Vitaly Zubialevich and Dinh Van Duc (postdoctoral research assistants), Zhiheng Quan, Shahab Norouzian andPietro Pampili (PhD postgraduate researchers).
Our interests are in the preparation and use of gallium nitride and its related materials for optoelectronic and electronic device applications. The material is “grown” as a crystal in thin layers on a substrate. The thickness of the layers can be controlled at the atomic scale, and the reactor allows precise control of the composition and doping of the layers in order to create the devices with the desired properties. The reactor can be seen among the pictures to the right; however, the bulk of the machine is made up of the plumbing that controls the flow of the Group III and Group V reaction precursors.
In particular we wish to develop high brightness ultraviolet emitters operating at wavelengths between around 240 and 340 nm for biotechnology applications, and for germicidal sources. These are very challenging to produce as the short wavelength of the light corresponds to high photon energies, meaning that materials that might traditionally be considered electrical insulators have to be encouraged to conduct electricity and emit light.
In addition to optoelectronic applications the same materials can be used to form transistors that allow operation with high power densities, and or with high frequencies. These have application for power electronics, to control electrical machines, or potentially to make compact power supplies for electronic devices. High frequencies are required for communication systems, for example in the base stations for mobile phone networks.
Characterization and testing
Once a structure has been grown, it can be characterized structurally and electronically using a variety of methods, some of which are described below
|X-ray diffraction, the equipment for which is pictured to the left, takes advanatage of Bragg's law by reflecting X-rays off the crystallographic planes intrinsic in the structure that requires characterization. Measuring the reflections gives information on the thickness and composition of the desired layer when compared with a simulation using the software on the depicted computer.