Dear Sreeprasad,

LEDs in this wavelength regime are not commercially available, even though the band gap of AlN is 6.2 eV (210 nm). The main problem is stability and light outcoupling of Al-rich (Al,Ga)N semiconductors.

Radiation sources for the wavelength range below 240 nm are indeed excimer lamps, e.g. KrCl* as a 222 nm emitter. A Xe2* excimer discharge emits at 172 nm, while the spectrum can be modulated by phosphors, e.g. YPO4:Nd (193 nm), LaPO4:Pr (225 nm), YPO4:Pr (235 nm), or YPO4:Bi (241 nm).

Ushio has some of these lamps in their portfolio.

All the best for your research,

Thomas

Dear Sreeprasad,

LEDs in this wavelength regime are not commercially available, even though the band gap of AlN is 6.2 eV (210 nm). The main problem is stability and light outcoupling of Al-rich (Al,Ga)N semiconductors.

Radiation sources for the wavelength range below 240 nm are indeed excimer lamps, e.g. KrCl* as a 222 nm emitter. A Xe2* excimer discharge emits at 172 nm, while the spectrum can be modulated by phosphors, e.g. YPO4:Nd (193 nm), LaPO4:Pr (225 nm), YPO4:Pr (235 nm), or YPO4:Bi (241 nm).

Ushio has some of these lamps in their portfolio.

All the best for your research,

Thomas

YPO4:Nd is having wavelength at 193 nm

You may check BaF2 scintillator crystals (they can be stimulated by X-ray or radioactive source), they emit some light below 240nm..

https://optics.org/products/P000022510

Thank you so much Thomas Jüstel , Jassim Abas Al-Hilfi and Nikolay Pavlov .