Development, fabrication and test of a highly segmented hybrid photodiode

Hybrid photodiodes (HPD) represent one of the most promising options for high granularity single photon detection. We report about the development of the Pad HPD, a 5-in. device with a bialkali photocathode and encapsulated analog electronics for the readout of the 2048 channels. The design of the Pad HPD was optimised for the use in the RICH detectors of LHCb. Several HPDs have been fabricated in a dedicated UHV facility at CERN. We briefly summarise the fabrication process and the excellent performance figures obtained in a lab set-up and with Cherenkov radiators in test beams. Emphasis is put on the performance increase which resulted from recent minor design changes.