DEPFET detector-amplifier structure: Properties, achievements and new developments, concepts and applications

The DEPFET detector-amplifier structure invented 1985 by J. Kemmer and G. Lutz possesses several unique properties which make it extremely interesting as readout element in semiconductor detectors and in particular as building block of semiconductor pixel detectors. DEPFET detectors of various kinds have been built at the MPI Semiconductor Laboratory in Munich with its high quality double sided silicon processing line. These devices include DEPFET pixel detectors to be used in two X-ray astronomy missions and a RNDR (repeated non destructive readout) structure which allowed to measure the signal charge with a precision of a quarter of the elementary charge. A common property of these detectors is the simultaneous measurement of position and energy of X-ray photons (spectroscopic imaging). Presented for the first time are pixel devices which allow selection of signal charges arriving in a predefined time interval. Charges produced outside this gate interval are lead to a sink electrode. Furthermore the selected charge can be stored for delayed readout. These devices are for example well suited for application in the field of adaptive optics. Another new concept is that of a DEPFET with stongly nonlinear device characteristics that allows to combine high resolution charge measurement with large dynamic range. It will be used for application at the new X-ray sources, the free electron laser XFEL.