Fill-factor improvement of Si CMOS single-photon avalanche diode detector arrays by integration of diffractive microlens arrays

摘要

Single-photon avalanche diode (SPAD) detector arrays generallyudsuffer from having a low fill-factor, in which the photo-sensitive area ofudeach pixel is small compared to the overall area of the pixel. This paperuddescribes the integration of different configurations of high efficiencyuddiffractive optical microlens arrays onto a 32 × 32 SPAD array, fabricatedudusing a 0.35 μm CMOS technology process. The characterization of SPADudarrays with integrated microlens arrays is reported over the spectral range ofud500-900 nm, and a range of f-numbers from f/2 to f/22. We report anudaverage concentration factor of 15 measured for the entire SPAD array withudintegrated microlens array. The integrated SPAD and microlens arrayuddemonstrated a very high uniformity in overall efficiency.