Indirect optical crosstalk reduction by highly-doped backside layer in PureB single-photon avalanche diode arrays

A method of reducing indirect optical crosstalk in a PureB single-photon avalanche diode (SPAD) array is investigated by TCAD simulations. The reduction is accomplished by taking advantage of the enhanced optical absorption of a highly-doped Si layer (p-type, 3×10
²⁰
cm
^-3
) on the backside of the wafer. The simulation environment is developed to give information about optical crosstalk by incorporating the experimental optical constants of the materials constituting the crosstalk reduction layer. It is shown that the indirect optical crosstalk is greatly reduced by increasing the thickness of the highly-doped Si layer. A crosstalk reduction of two orders of magnitude is gained with addition of the PureB/a-Si stack.