Blue light-emitting diode in the industry led to the lighting industry revolution

The industry generally believe that the semiconductor light-emitting lamp to replace the traditional lamp, as the semiconductor transistor to replace the vacuum tube as significant and far-reaching." Professor Jiang Fengyi director of light-emitting materials and Devices Engineering Research Center of Ministry of education, told reporters: "we have successfully developed a GaN blue silicon substrate light emitting diode materials and devices, now the test has been completed, the ongoing pilot."

According to reports, the light emitting diode (LED) is a cold light source, and the voltage of about 3 volts current on the magnitude can send certain colors of light, is one of the main components of the field of electronic information technology. In the past, it was often used for the indication, display and transmission of various industrial equipment, instruments, communications, transportation, finance, household appliances, indoor and outdoor decoration, etc.. If you use it to replace the traditional lighting to light, what are the benefits?

Theoretically, the luminous efficiency of semiconductor lighting can reach even more than 10 times the incandescent lamp, fluorescent lamp 2 times. Therefore, the utility model has the remarkable energy saving effect." Jiang told reporters, "at the same time, it has small size, can be made into various shapes; directional, bright color; firm structure, impact resistance and strong seismic ability; long life, up to 100000 hours; no infrared and ultraviolet radiation; mercury free, is conducive to environmental protection and other advantages."

The main scheme of manufacturing semiconductor lighting lamp is to use blue light to excite rare earth phosphor to synthesize white light. As a result, the blue light-emitting diode becomes the core part.

Jiang: "blue LED several existing preparation techniques have some shortcomings, such as the current dominant" sapphire substrate GaN based LED ", although still improve the material growth and device manufacturing level, but the sapphire substrate is not conductive, poor thermal conductivity, scribing difficulties, antistatic ability, flip chip technology the complex, and the lateral resistance, high current density under high working voltage, a waste of energy, is not conducive to the advance of semiconductor lighting technology. The silicon carbide substrate GaN based LED ", because of its substrate thermal conductivity, in the semiconductor lighting chip advantage, the other leading technology solutions within a certain time, but its price is high, the difficulty of scribing. In addition, the GaN substrate GaN based 'LED', the quality of the epitaxial material can be significantly improved, but there is also a problem of high prices, and device processing is also a problem. In this case, the silicon substrate has become the focus of attention of researchers."

For the preparation of light emitting devices on a silicon substrate by Jiang "it is in the field of Optoelectronics dream one thing" to describe. Compared with sapphire and silicon carbide substrate, silicon wafer as the substrate of GaN material has many advantages, such as good conductivity, thermal conductivity, high crystal quality, large size, low cost, easy processing, etc.. However, due to the large lattice mismatch and thermal mismatch between the GaN epitaxial material and the silicon substrate, it is very difficult to obtain the device quality GaN material on the silicon substrate. Although in recent years, the preparation of more GaN materials and devices has been reported on the silicon substrate, such as the United States, Germany, Japan and other countries have successively developed on silicon substrate GaN based LED, but reported the highest output power is only 2mW, compared with the sapphire is not on the quality of the materials and devices.

However, the dream of scientists in the field of luminescent materials and Devices Engineering Research Center has become a reality. The National 863 plan, 863 plan special nano optoelectronics and other key topics under the auspices of the center on silicon substrate developed GaN blue light emitting diode epitaxial materials and devices, the two inch wafer within the working voltage of the chip of LED is less than 3.5V, the light output power of more than 5mW, won the practical performance of Si substrate GaN the blue LED device, the main performance index is better than similar devices in the current level reported in the literature.

"That this breakthrough on silicon substrate epitaxial GaN LED, originally feared" cracking, poor crystal quality and P type doping, high working voltage, low luminous intensity, poor reliability can overcome all the problems of all. "." Jiang said, "especially the technical route has a very big advantage in the welding strip, easy to manufacture high reflective layer P contact electrode and high N surface light rate, reduce working voltage, no lateral resistance easy to work in a high current density, easy to heat, antistatic ability."

It is reported that the results of the April 2005 Xiamen semiconductor lighting international forum after the report, the international peer evaluation of experts for the best international results. The domestic experts for the evaluation of the results: the successful development and has the international first-class level of silicon substrate blue diode materials and devices, and has great practical significance and value for the development of industry in China in the field of light-emitting materials and devices.

In the laboratory, Jiang told reporters the GaN blue light emitting diode silicon substrate. As the power is turned on, the small diode emits a brilliant light, though it is the day, still dazzling. He said: "if it is sapphire, to achieve this brightness is normal, but it is not easy to use silicon. We are working with the strength of the investment side of the industrial cooperation negotiations for the end of this product to market."