Measurement results of different options for spectroscopic X-ray DEPFET sensors

The challenging demands of recent experiments in X-ray astrophysics promoted the development of DEPFET detectors. Their excellent performance is based on an intrinsic signal amplification, which is implemented for each active pixel. Most recently, prototypes of spectroscopic X-ray DEPFETs were investigated for the Wide Field Imager of ESA's next X-ray telescope Athena. For this reason, a dedicated prototype production of DEPFET sensors, comprising different technology options was fabricated and assembled to detector modules. In this paper we compared different sensor technology options and studied the spectroscopic performance on 64 × 64 pixel detectors. The sensors feature an identical layout but were taken from different wafers, which undergo specific manufacturing processes. These processes concern the thickness of the oxide underneath the transistor gate, the etching of the transistor gate and different surface implantations. Each process is correlated to the investigated properties of the corresponding detectors, which makes the detector best suited for specific applications. In particular DEPFET properties, concerning the clear behaviour, short channel effects or charge amplification are analysed. The studies are complemented by results of spectral measurements and electrical characterization.