Fabrication of PureB-only light-entrance windows for VUV sensitive single-photon avalanche diodes

Single-photon avalanche diodes (SPAD) fabricated in PureB (Pure Boron) technology can be made sensitive to the whole vacuum-ultraviolet (VUV) light range from 10 nm – 400 nm if a PureB-only light-entrance window is realized. Different techniques for doing this are evaluated in terms of the device electrical performance in relationship to the effect of the processing on the PureB layer itself. A very low noise SPAD can be achieved when the as-deposited PureB layer is not significantly modified by the subsequent processing.