A new generation of white LED debut

French scientists have shown that the single crystal (monolithic) white light emitting diode (WLED) performance is expected to exceed the previous use of composite manufacturing technology WLED. CRHEA-CNRS Benjamin Damilano and its research team using gallium nitride (GaInN) / gallium nitride (GaN) quantum wells to produce blue and yellow light, and then make a WLED. This result makes the commercialization of WLED has a step forward, the future is expected to replace the current use of incandescent bulbs. Scientists have been working on the WLED for nearly ten years, hoping to produce a high efficiency, long life and cheap solid-state WLED, in order to compare with the current high energy consumption of incandescent bulbs or fluorescent lamps. Although the luminous efficiency of 200 lm/W WLED has come out, but compared with the traditional light source, the cost is still high.

Recently, many research teams, including CRHEA-CNRS, have confirmed that a single crystal WLED can be fabricated by stacking gallium nitride or gallium nitride quantum wells in the gallium nitride p-n interface. The so-called single crystal refers to the use of continuous epitaxial growth of a single method to replace the traditional production of phosphorescent WLEDs dual method (epitaxy and deposition). This technology can not only reduce costs, but also improve product reliability.

CRHEA-CNRS team with the help of the electronic active area of the p-n interface in the assembly of different thickness of the quantum well, to produce blue and yellow light, after mixing can produce white light. However, there is a flaw in the design: the light is very sensitive to the changes in the injected current, so the luminous efficiency of the components is limited by the yellow light quantum wells.

Novel design of white light converter

In order to solve this problem, quantum well team will produce yellow light produced in the p-n interface, it is no longer in current excitation of this quantum well, but the use of blue photons to excite, in other words, the injected current active area in electron and hole recombine emit blue light, yellow light blue photon will be part of quantum well absorption and stimulate the yellow light, and white light mixed produce white light. Damilano said that the key to this technology is that it saves the single crystal architecture, but the application is more flexible than the original structure.

At present, the team plans to use other than the InGaN Quantum well structure is more efficient as quantum dots to achieve optical conversion they consider to replace the sapphire substrate current to the substrate, to reduce the manufacturing cost components.