Abstract: A single photon avalanche diode for use in a CMOS integrated circuit includes a deep n-well region formed above a p-type substrate and an n-well region formed above and in contact with the deep n-well region. A cathode contact is connected to the n-well region via a heavily doped n-type implant. A lightly doped region forms a guard ring around the n-well and deep n-well regions. A p-well region is adjacent to the lightly doped region. An anode contact is connected to the p-well region via a heavily doped p-type implant. The junction between the bottom of the deep n-well region and the substrate forms a multiplication region when an appropriate bias voltage is applied between the anode and cathode and the guard ring breakdown voltage is controlled with appropriate control of the lateral doping concentration gradient such that the breakdown voltage is higher than that of the multiplication region.

Abstract: A deep SPAD structure uses the substrate as the anode terminal of its multiplication p-n junction. A bias voltage for the SPAD (in excess of the SPAD's breakdown voltage) is coupled to the SPAD's cathode terminal. The bias voltage is generated by a charge pump circuit which is also integrated on the substrate. The charge pump circuit is configured to isolate the bias voltage on the cathode terminal. A triple well CMOS process is used to isolate the transistors of the charge pump circuit from the substrate.

Abstract: A single photon avalanche diode for use in a CMOS integrated circuit includes a deep n-well region formed above a p-type substrate and an n-well region formed above and in contact with the deep n-well region. A cathode contact is connected to the n-well region via a heavily doped n-type implant. A lightly doped region forms a guard ring around the n-well and deep n-well regions. A p-well region is adjacent to the lightly doped region. An anode contact is connected to the p-well region via a heavily doped p-type implant. The junction between the bottom of the deep n-well region and the substrate forms a multiplication region when an appropriate bias voltage is applied between the anode and cathode and the guard ring breakdown voltage is controlled with appropriate control of the lateral doping concentration gradient such that the breakdown voltage is higher than that of the multiplication region.