Development and prototyping of the DEPFET active pixel detector (June 2013)

Active pixel sensor composed of DEPFETs (DEPleted Field Effect Transistors) array has been developed by DEPFET collaboration. The concept of DEPFET was proposed by Kemmer and Lutz in 1987 and today, it was developed into state-of-the-art highly granular, ultra-transparent monolithic pixel detectors for vertex reconstruction at future collider experiments. Excellent signal over noise performance is provided by integration of a MOSFET (Metal Oxide Semiconductor Transistor) in each pixel, which works as the first amplification stage of readout electronics. Thinning technologies make it possible to manufacture DEPFET sensors with thickness of active sensor area 50-75 micrometers. Steering ASICs (Application-Specific Integrated Circuits) as well as test systems were developed to characterize and optimize the DEPFET sensors. The DEPFET detector is being developed as a vertex detector at Belle II experiment at the electron-positron SuperKEKB collider in Japan and the future International Linear Collider, but the concept of the DEPFET sensor offers also other fields of applications. In this paper the key parameters of the sensor design are presented, together with the individual ASICs. Furthermore, results of the prototypes tested using radioactive source, and laser are shown.