Triple epitaxial single‐photon avalanche diode for multichannel timing applications

Abstract

In the last years, custom-technology single-photon avalanche diodes (SPADs) have demonstrated remarkable performance, thanks to the fine engineering process performed on the electric field profile. However, the integration of custom SPADs in detector arrays often conflicts with the low-threshold current sensing that is mandatory to extract the timing information. A new custom-technology SPAD is introduced, that exploits an extra epitaxial layer in order to reduce the capacitive coupling between the anode and the chip substrate. The new detector shows a state-of-the-art timing jitter of 34 ps full width at half maximum and a weak dependence on the detection threshold, even when the substrate is kept at a fixed voltage, as required by the implementation of multichannel photon timing systems.

Recent Advances and Future Perspectives of Single‐Photon Avalanche Diodes for Quantum Photonics Applications

“…[ 72 ] This issue can make the design of the front end circuit particularly challenging to achieve low‐threshold operation, especially if no solutions are used to minimize such parasitic capacitance. [ 73 ]…”

“…However, this modification results in a higher breakdown voltage, that increases from about 35 V for a thin SPAD up to 70 V for a RE‐SPAD, and in a larger overvoltage, that increases from a few volt up to 20 V. In order to fully accommodate such higher voltages it is necessary, on the one hand, to avoid the edge breakdown by introducing guard rings around the cathode diffusion and, on the other hand, to increase the breakdown voltage of the substrate junction by interposing a lightly‐doped n‐layer between the n+ substrate and the p+ buried layer. Moreover, this additional layer reduces also the capacitive parasitics of the junction, [ 73 ] with beneficial effects in terms of both timing jitter and afterpulsing. Unfortunately, the increased thickness of the quasi‐intrinsic layer also prevents the n+ isolation from reaching the n+ substrate, resulting in a SPAD that is no more electrically isolated from the rest of the substrate and, thus, that can not be employed in detector arrays of fully independent pixels.…”

Recent advances and future perspectives of single-photon avalanche diodes for quantum photonics applications

“…Therefore, the substrate must be biased at a fixed potential, making the substrate capacitance a viable path where the avalanche current can get lost [78]. This issue can make the design of the front end circuit particularly challenging to achieve low-threshold operation, especially if no solutions are used to minimize such parasitic capacitance [79].…”

“…However, this modification results in a higher breakdown voltage, that increases from about 35 V for a thin SPAD up to 70 V for a RE-SPAD, and in a larger overvoltage, that increases from a few volt up to 20 V. In order to fully accommodate such higher voltages it is necessary, on the one hand, to avoid the edge breakdown by introducing guard rings around the cathode diffusion and, on the other hand, to increase the breakdown voltage of the substrate junction by interposing a lightlydoped n-layer between the n+ substrate and the p+ buried layer. Moreover, this additional layer reduces also the capacitive parasitics of the junction [79], with beneficial effects in terms of both timing jitter and afterpulsing. Unfortunately, the increased thickness of the quasi-intrinsic layer also prevents the n+ isolation from reaching the n+ substrate, resulting in a SPAD that is no more electrically isolated from the rest of the substrate and, thus, that can not be employed in detector arrays of fully independent pixels.…”

37ps-Precision Time-Resolving Active Quenching Circuit for High-Performance Single Photon Avalanche Diodes

“…The main task of the pick-up circuit is collecting all the avalanche current while keeping the detector anode at a fixed voltage. This aspect is of the utmost importance to prevent any current loss due to the SPAD anode-substrate capacitance, that is in the order of a few picofarad (depending on the characteristics of the detector [22]). Since the lower the current threshold used to sense the avalanche, the lower the timing jitter of a custom-technology SPAD [23], the minimization of the current loss is crucial.…”