Solar blind UV photodiodes with 100% internal quantum efficiency based on silicon direct band gap

5 mm diameter silicon photodiodes having 30-50 nm electrically active thicknesses were fabricated on silicon-on insulator (SOI) wafers to realize solar blind UV photodiodes (UVTN). Their responsivity measurements in the 200-1100 nm range indicated that responsivities drop sharply after 350 nm. Silicon direct bandgap is 3.5 eV which corresponds to 354 nm. Thus, these devices act as wide band gap semiconductor photodiodes like SiC, GaN, AlGaN, diamond etc. UV/VUV/EUV filters can be directly deposited on UVTN detectors to limit their response to specific wavelengths. Four filtered UVTN photometers devoid of chronic red leak and associated electronics will fit in a 1 U CubeSat which can be used to make solar UV/VUV/EUV spectral measurements. Because of their minuscule silicon thickness, UVTN detectors will have low responsivity to x-rays and other space radiation and also will be very hard to space radiation. Thus, these devices are expected to survive in the deep space environment for several decades for applications like water detection (165 nm strong reflection) on small bodies as desired by NASA’s Small Bodies Assessment Group. As the solar blind material is silicon which is high volume manufacturing compatible, this is a disruptive technology development and will have numerous application in space research. For example, one may use UVTN pixels in an imaging array to get a true solar blind (no red leak) UV/VUV/EUV imager with 100% IQE.