Speaker
Description
We propose a novel APD array showing near 100% fill factor. The APDs operate in proportional mode at low or moderate gain and exhibit very high detection efficiency also in inter pixel gap regions. By applying a fully depleted reach-through structure light entrance side and electronics side are kept separated. In contrast to common APD arrays the avalanche process is sustained in the inter pixel gap regions as well. A non structured boron doped multiplication region (MR) extends over the entire array. Parasitic early breakdown at the n+ pixel edges is caused by electric field peaks near to convex doping shapes. In our approach it is suppressed by a n-doped layer, called field drop region (FDR), located directly beneath the n+ pixels. The positive space charge of this fully depleted layer causes a reduction of the electric field to a non-critical level when it reachs the n+ edges. The FDR gets depleted by the negative MR space charge preventing pixel shortage. We started a first prototyping on 450µm thick p-type float zone. Measures for excess noise reduction are implemented to optimize the sensor for photon science applications. For MR a high energy implantation was chosen. The peak concentration is in a depth of about 6µm. Due to the wider MR a lower electric field is required to achieve the same gain. Lower electric field results in a smaller k value (hole/electron ionization rate) and lower excess noise. Since MR and FDR implantations are lithographically confined to the area of the APD array a classical multi guard rings can be used for edge termination. The prototype design contains small pixel and strip arrays for eta-plot measurements. We will present a detailed description of the operating principles and plan to compare first measurements with simulations.
| Submission declaration | Original and unplublished |
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