GaN Substrate Will Lead The Development Trend of LED

Compared with conventional substrate material , gallium nitride has a large band gap , high breakdown voltage , large thermal conductivity , high saturated electron drift velocity , strong anti-radiation and good chemical stability superior characteristics , is by far the theory lightning highest photoelectric conversion efficiency of the material system. GaN substrate relative to sapphire, silicon carbide substrate obvious performance advantages , but the biggest problem is that the price is too high.

Thick film substrate products : products are 10 to 50 microns in different sizes , commonly used is 20 to 30 microns. Dislocation density 107cm^-3order of magnitude, depending on the technical parameters can be divided into two kinds i.e., semi-insulating and n -type doped . n -type doping is mainly used in LED and other optoelectronic devices, used primarily on semi-insulating power electronics, microwave devices.

Aspects of the self-supporting substrate of GaN : dislocation density 105cm ^-3 order of magnitude, depending on the technical parameters are divided into three types , i.e. n -type dopant , and the non -doped semi-insulating . n -type GaN , mainly used in LED, lasers ; semi-insulating then applied to the high-power microwave devices or high-current high- voltage switch. That undoped GaN high purity applications more widely on the detector , electron density material requirements as low as possible . Navier undoped GaN products , X-ray ( 002 ) peak half- width of 50 seconds ( 102 ) peak half- width of about 80 seconds , the electron mobility of the bulk material over 1500cmV-1s-1, the forefront in the international level. Navi is internationally one of the few capable of producing self-supporting unit sales of gallium nitride wafer .

HVPE grown GaN self- supporting substrate z

HVPE mainly metal gallium, hydrogen , ammonia, and hydrogen chloride reacts metallic gallium to form gallium chloride , gallium chloride gas after 200 ℃ becomes to the raw materials , and then on the substrate surface by reaction with ammonia becomes GaN . This generation HVPE method, the surface of the chemical saturation is very high, therefore, the growth rate is very fast , 50 to 100 times faster than the MOCVD growth rate , it is possible to grow one hour from 200 to 300 microns, in a short time the quality of this material becomes GaN , which is one of its characteristics.

The next five years , the price will drop GaN 10 to 20 times , 4 to 6 inches into the market

Heteroepitaxial on homoepitaxial GaN on sapphire substrate with the substrate , from a technical perspective, the hetero-epitaxial defect density GaN homoepitaxial higher than the 2 to 3 orders of magnitude. GaN has a conductive characteristics, the vertical structure of the chip can be made , so that the use of epitaxial wafer area increased 1.5 times higher than sapphire . After forming the vertical structure , the high current density GaN , a desired GaN substrate chip on the chip can be arrived ten sapphire substrate . United States and Japan NGK Sorra has begun to vigorously develop such chips, and made ​​an important breakthrough , to achieve the same brightness, the GaN substrate produced low energy consumption than traditional LED chips more than half.

With the decline in the amount of gallium nitride -scale production and prices , as well as the continuous development of LED epitaxial technology, the chip when the current density increased to 5 to 10 times, the use of GaN LED on sapphire obvious advantages than many . The next five years , prices for LED GaN substrate can drop 10 to 20 times, gallium nitride substrate in the unit price will be made ​​lumens significant advantage .


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