Research Fellows Directory
Dr Rachel Oliver
University of Cambridge
Light emitting diodes (LEDs) are found in lots of the electrical equipment you use every day. Perhaps, when you press the “standby” button on your CD player a little red light comes on? That’s an LED! White LEDs are now available which could replace the light bulbs all around your home, saving you lots of money on your energy bills. LED lighting units are about five times more energy efficient than a standard light bulb, and in the future they may be more efficient still. This could result in significant reductions in energy usage and greenhouse gas emissions, since, surprisingly, 20% of the electricity generated in the UK is used for lighting.
White LEDs are made using an unusual material called gallium nitride (GaN). GaN is a semiconductor – the same class of material as silicon, which is used to make computer chips. However, silicon can be made in very large quantities, and the material which is produced today is almost perfect. GaN, on the other hand, is usually produced as very thin layers which are deposited onto another material. As a result of this process, the GaN structure is not perfect like silicon but instead is full of mistakes or “defects”. These defects are very tiny, but can have a profound effect on how well an LED works. Hence, my research focuses on developing methods to measure and understand the structure of GaN (and other materials which are used in LEDs) at a very small scale.
Armed with this understanding, I will be able to determine what factors control how efficient LEDs are and how long they can operate for without breaking. Hence, I’ll be able to design new LED structures which are more efficient and last for ages, and will thus be really attractive for people to buy to light their homes in an environmentally-friendly way. Also, I hope to design new light sources using GaN that can be used in other ways, such as in secure communications or in the computers of the future, which may process information using only light.