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“These organometal halide perovskites are remarkable semiconductors,” said Zhi-Kuang Tan, a PhD student at the University of Cambridge’s Cavendish Laboratory and the paper’s lead author. “We have designed the diode structure to confine electrical charges into a very thin layer of the perovskite, which sets up conditions for the electron-hole capture process to produce light emission.”
Spin-coating
The perovskite LEDs are made using a simple and scalable process in which a perovskite solution is prepared and spin-coated onto the substrate. This process does not require high temperature heating steps or a high vacuum, and is therefore cheap to manufacture in a large scale. In contrast, conventional methods for manufacturing LEDs make the cost prohibitive for many large-area display applications.
“The big surprise to the semiconductor community is to find that such simple process methods still produce very clean semiconductor properties, without the need for the complex purification procedures required for traditional semiconductors such as silicon,” said Richard Friend of the Cavendish Laboratory, who has led this programme in Cambridge.
“It’s remarkable that this material can be easily tuned to emit light in a variety of colours, which makes it extremely useful for colour displays, lighting and optical communication applications,” said Tan. “This technology could provide a lot of value to the ever growing flat-panel display industry.”
The team is now looking to increase the efficiency of the LEDs and to use them for diode lasers, which are used in a range of scientific, medical and industrial applications, such as materials processing and medical equipment. The first commercially- available LED based on perovskite could be available within five years.
Imec demonstrates 28Gb/s photonics platform III-V laser integration still in the laboratory
Imec has reached some key development milestones for its silicon photonics platform (iSiPP25G) by extending the performance towards 28Gb/s and beyond.
At wafer-scale, it has demonstrated a ring-based wavelength division multiplexing (WDM) filter with a thermo-optic tuning efficiency better than 1nm/ mW per channel; a thermally tunable 28Gb/s ring modulator with an efficiency of 260pm/mW; and a high-speed germanium photodetector achieving an average responsitivity of 0.85A/W, and opto- electrical bandwidth of 50GHz with dark currents at -1.0V below 50nA.
Silicon photonics holds the promise of converging electronics and photonics, but a key component still missing within such a platform is a low-cost high-performance laser. IMEC is considering adding III-V lasers to the platform in the future by hybrid approaches such as flip-chip bonding. It is also exploring adding monolithically integrated lasers using InP-nanowires lasers and colloidal quantum dots.
Last year, researchers from IMEC and the University of Ghent presented the first room- temperature operation of an ultra-short InP nanowire laser that is epitaxially grown on an exactly [001] oriented silicon substrate. In May 2014, the team gave a paper at the International Conference on Indium Phosphide and Related Materials(IPRM) showing an improvement of the device with ultra low threshold performance.
‘An Ultra-Short InP Nanowire Laser Monolithic Integrated on (001) Silicon Substrate’, by Z. Wang et al was presented at IEEE summer topicals 2013.
‘InP Nanowire lasers Epitaxially Grwnn on (001) Silicon ‘V- groove’ templates’, by B. Tian et al was presented at the International Conference on Indium Phosphide and Related Materials(IPRM) 2014.
Issue VI 2014
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