Japan's two universities cooperate to develop 227.5nm UV LED
A research team composed of the Japan Institute of Physical Chemistry and Saitama University developed an ultraviolet LED with a wavelength of 227.5 nm and an output of 0.15 mW.
To date, other research teams have reported UV LEDs with a wavelength of 210 nm, but their output is only 0.02 μW. This time, the research team not only introduced the 227.5nm UV LED prototype, but also successfully developed a UV LED prototype with a wavelength of 253nm output of 1mW, a wavelength of 261nm output of 1.65mW and a wavelength of 273nm output of 3.3mW. According to the research team, the output of these UV LEDs is substantially equivalent to the output of the blue, red, and white LEDs used by the bulb, and meets the output levels required for the germicidal lamp.
The research team composed of RIKEN and Saitama University used AlGaN semiconductor materials in the preparation of UV LEDs. The AlN layer was first formed on the sapphire substrate, and then the n-type AlGaN layer and the AlGaN light-emitting layer (three-quantum well structure) were sequentially stacked. And a p-type AlGaN layer. In addition, the research team improved the method of growing AlN layers on sapphire substrates. The new method formed multiple AlN layers by alternately using two different growth methods: First, the Al material was continuously supplied to generate a layer when intermittently supplying ammonia gas. The AlN layer is then further supplied with ammonia and Al to form another layer of AlN.
This growth method is called an ammonia pulsed supply multiple layer growth method, which has the advantages of reducing the line dislocation density of the AlN layer, increasing the smoothness of the crystal layer, and reducing cracks caused by crystal deformation. . Since the quality and smoothness of the AlN layer are improved, the quality and smoothness of other layers formed on the AlN layer are also improved, and the output of the AlGaN light-emitting layer is thus increased by nearly 50 times.
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