MARTHA - Monolithic Array of Reach THrough Avalanche photo diodes

We propose a novel APD array showing 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 layer (ML) extends over the entire array. An n-doped field drop layer (FDL), which is located directly under the n + pixels, suppresses the peaks of the electric field at the n + pixel edges and thus the edge breakdown. The positive space charge of this fully depleted layer reduces the electric field at the n + edges to a non-critical value. The FDL gets depleted by the negative ML space charge, which prevents pixel shortage. A prototyping on 450 μ m thick p-type float zone has just been finished. Measures for excess noise reduction have been implemented to optimize the sensor for photon science applications. Since ML and FDL implantations are lithographically confined to the area of the APD array a classical multi guard ring structure could be used for edge termination. The prototype design contains diodes, small pixel and strip arrays for eta-distribution [1] measurements. First I-V measurements are presented.