A new semiconductor device capable of emitting two distinct colours has been created by a group of researchers in the US, potentially opening up the possibility of using light emitting diodes (LEDs) universally for cheap and efficient lighting.
The proof-of-concept device, which has been presented today, 3 May, in IOP Publishing's journal Semiconductor Science and Technology, takes advantage of the latest nano-scale materials and processes to emit green and red light separated by a wavelength of 97 nanometresa significantly larger bandwidth than a traditional semiconductor.
Furthermore, the device is much more energy efficient than traditional LEDs as the colours are emitted as lasers, meaning they emit a very sharp and specific spectral linenarrower than a fraction of a nanometrecompared to LEDs which emit colours in a broad bandwidth.
One of the main properties of semiconductors is that they emit light in a certain wavelength range, which has resulted in their widespread use in LEDs. The wavelength range in which a given semiconductor can emit lightalso known as its bandwidthis typically limited in the range of just tens of nanometres. For many applications such as lighting and illumination, the wavelength range needs to be over the entire visible spectrum and thus have a bandwidth of 300 nm.
Single semiconductor devices cannot emit across the entire visible spectrum and therefore need to be 'put' together to form a collection that can cover the entire range. This is very expensive and is, to a large extent, the reason why semiconductor LEDs are not yet used universally for lighting.
In this study, the researchers, from Arizona State University, used a process known as chemical vapour deposition to create a 41 micrometer-long nanosheet made from Cadmium Sulphide and Cadmium Selenide powders, using silicon as a substrate.
Lead author of the study, Professor Cun-Zheng Ning, said: "Semiconductors
|Contact: Michael Bishop|
Institute of Physics