Multi-junction pico-avalanche detector
The present relates to a multi-junction photon detector comprising a semiconductor substrate, a plurality of n+ pixels on the top surface and a p+ uniform doping implant on the backside and at least one n-doped layer on the backside, deeper in the substrate bulk than the p+ implant, such that the detector presents a first PN junction corresponding to a drift and signal induction region and comprising the pixels on the substrate, and a second PN junction corresponding to a gain region and comprising the n-doped layer disposed on the backside of the detector active area deeper in the substrate bulk. These two junctions are operated in inverse polarization. The area between them contains a PN junction in direct polarization and it is fully depleted from the free charges.
1. Multi-junction photon detector comprising
a silicon substrate presenting a drift region in the bulk ( 1 ),
a plurality of pixels ( 2 ) on the top surface of the silicon substrate,
a uniform doping implant ( 3 ) on the backside surface of the substrate and
at least one deep implant layer ( 4 ) on the backside, deeper in the substrate bulk than the uniform doping implant such that the drift region ( 1 ) and the deep implant layer ( 4 ) are interposed between the plurality of pixels ( 2 ) and the uniform doping implant ( 3 ),
wherein, in use, the detector presents a first junction in inverse polarization, corresponding to the interface between the pixels ( 2 ) and the drift region in the substrate ( 1 ), and
a second PN junction in inverse polarization between the deep implant layer ( 4 ) and the uniform doping implant ( 3 ) on the backside surface forming a gain region,
wherein both the plurality of pixels ( 2 ) and the uniform doping implant ( 3 ) function as end terminals, generating a current signal between them and directing said current signal through the drift region ( 1 ) and the deep implant layer ( 4 ) responsive to photons at the pixels.
2. Multi-junction photon detector according to claim 1 , characterized in that the first junction is a PN junction in inverse polarization where the silicon substrate is a lightly p-doped or intrinsic silicon substrate and the pixels are n-doped.
3. Multi-junction photon detector according to claim 1 , characterized in that the second junction is a PN junction in inverse polarization formed between a deep n-doped layer ( 4 ) and a uniform p+ doped region ( 3 ) in the backside surface of the substrate.
4. Multi-junction photon detector according to claim 1 , characterized in that it comprises a third junction in direct polarization between the drift region and the deep n-doped implant layer on the back side.
5. Multi-junction photon detector according to claim 1 , characterized in that the second PN junction in inverse polarization corresponds to a gain layer that covers uniformly the backside of the sensor active area.
6. Multi-junction photon detector according to claim 1 , characterized in that the second PN junction in inverse polarization is operated at a field high enough to generate impact ionization from the charge carriers.
7. Multi-junction photon detector according to claim 1 , characterized in that a region between the backside contact of the sensor and the gain layer is a photon absorption layer which can be modulated in thickness.
8. Multi-junction photon detector according to claim 1 , characterized in that it comprises multiple PN-junctions in the gain region.
9. Multi-junction photon detector according to any one of claim 1 , characterized in that the pixel matrix is surrounded by a guard ring structure.
10. Multi-junction photon detector according to claim 1 , characterized in that it is integrated with the electronics in a CMOS or a BiCMOS process.
11. Multi-junction photon detector according to claim 1 , characterized in that it is integrated with the electronics in a SiGe BiCMOS process.
12. Multi-junction photon detector according to claim 1 , characterized in that the gain region is structured in impact layers and thermalisation layers.