Solar Blind UV Silicon Photodiodes with Narrow Band Interference Filters

Fabrication of stable, 100% internal quantum efficiency (IQE) silicon photodiodes for 5 nm to 400 nm photons was successfully demonstrate decades ago. The 100%  IQE indicates that there is no photogenerated carrier loss in the p-n junction or at the device surface making possible complete collection of the signal by an external circuit. Owing to their unique characteristics, these are being used by national laboratories like  NIST and PTB  as transfer standards in the 5 - 250 nm region and by scientists for space and scientific applications worldwide. These devices  have 25 µm thick silicon carrier collection region. In the proposed phase I research, these devices will be made with 50 nm effective (electrically active) silicon thickness (Model UVTN) which will reduce their response to visible light by orders of magnitude keeping the same response to UV/VUV photons. To get the specified rejection of visible light by at least a factor of 105 ,  UVTN photodiodes will be used with a commercial  interference filter to achieve 280 nm bandpass (UVTN280) and with Al/Al2O3 multilayer filter and a commercial filter to achieve 247 bandpass (UVTN247).  Active area of the device will be 5 mm diameter for ease in manufacturing and testing.   In the Option Phase, fabrication of UVTN devices with Al/MgF2 multilayer filter for 135 nm passband (UVTN135)  is proposed. The fabricated devices are expected to have higher UV/VUV responsivity and lower or comparable  visible light response compared to the response of the diamond  detectors used  in LYRA onboard PROBA2 small satellite.