Single Photon Avalanche Diode with Double Charge Layers Based on Standard CMOS Process

A single-photon avalanche diode with double charge layers is designed with 180 nm standard CMOS technology, which is able to improve photon detection efficiency. PN junction is formed by deep N-well with retrograde doping P-charge layer. The different doping concentration of P-charge layers are selected to optimize the breakdown voltage. When the P-charge layer concentration is 1 x 10(18) cm(3), the simulation results show that the breakdown voltage is 17.8 V and the electric field intensity is 5.26 x 10(5) V/cm. Further study shows that the position of N-charge layer affects drift current density and diffusion current density. The device performance is optimal when the N-charge layer is doped at the contact of the deep N-well and the N isolation layer, in other words, when the peak of the N-charge layer is 2.5 mu m from the surface of the device. By using Silvaco TCAD simulation analysis, which can get a conclusion that at a wavelength of 500 nm, the detection efficiency peak is 62 % under bias voltage of 1 V, while the photon detection efficiency in the range of 300 nm to 700 nm is greater than 30 %.