Researchers in Japan have developed a new photodiode that can detect in just milliseconds a certain type of high-energy ultraviolet light, called UVC, which is powerful enough to break the bonds of DNA and harm living creatures. The researchers describe their new device in the journal Applied Physics Letters.
This is a crystal model of beta-Ga2O3.
Although this radiation doesn't normally reach the Earth's surface, it can leak through to just below the hole in the ozone layer. Monitoring this radiation is a way of tracking the hole in the ozone layer, and photodiodes that measure UVC are also used as flame sensors and for communication in space.
Now, Shinji Nakagomi and colleagues at Ishinomaki Senshu University in Japan have built a new kind of photodiode that can detect the whole range of UVC light while remaining insensitive to visible light from the sun -- two features that have eluded designers of current devices. By being "solar blind," photodiodes are more sensitive to the UVC range and are thus more useful.
Instead of a photodiode based on a conventional p-n junction, the researchers built one based on what's called a heterojunction, which is a p-n junction that incorporates two different semiconductors. The team used gallium oxide and silicon carbide, and found that their device responds quickly to UV light -- within milliseconds -- and has little dark current, which is the intrinsic electrical current that flows through the device even in the absence of light. Minimal dark current is important for a sensitive photodiode.
"The most important aspect about our device is that it is based on a heterojunction between gallium oxide and silicon carbide," said Nakagomi. "This gallium oxide and silicon carbide photodiode is promising for the detection of UV light."
The paper, "Deep ultraviolet photodiodes based on â-Ga2O3/SiC Heterojunction" is authored by Shinji Nakagomi, Toshihiro Momo, Syuhei Takahashi, and Yoshihiro Kokubun and appears in the journal Applied Physics Letters. See: http://dx.doi.org/10.1063/1.4818620ABOUT THE JOURNAL
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