Wednesday, May 04, 2016

DEPFET Pixel Said to Beat 1/f Noise

The open source Sensor journal publishes a sub-electron sensitive image sensor paper "The DEPFET Sensor-Amplifier Structure: A Method to Beat 1/f Noise and Reach Sub-Electron Noise in Pixel Detectors" by Gerhard Lutz, Matteo Porro, Stefan Aschauer, Stefan Wölfel, and Lothar Strüder from 1 PNSENSOR GmbH, München D-81739, Germany.

"The repetitive non-destructive readout (RNDR) DEPFET is an ideal central element for an active pixel sensor (APS) pixel. The theory has been derived thoroughly and results have been verified on RNDR-DEPFET prototypes. A charge measurement precision of 0.18 electrons has been achieved. The device is well-suited for spectroscopic X-ray imaging and for optical photon counting in pixel sensors, even at high photon numbers in the same cell."

The concept of a DEPFET: The signal
electrons are collected in a potential minimum
(internal gate) located below the channel of a
FET located on top of the fully depleted bulk.

Thanks to BB for the link!


  1. This is another installment in the Special Issue on Photon Counting Image Sensors co-sponsored by MDPI and the Int. Image Sensor Society. About of 1/3 of the papers have been reviewed and published so far. The papers are published as soon as they are accepted. (Guest Editors Fossum, Charbon, Teranishi, Theuwissen and Stoppa)

  2. "Due to the higher amplification a read noise of only 3.1 e− r.m.s. was obtained for a single readout and consequently a noise of 0.18 e− r.m.s. at a temperature of −55 °C was achieved after only 300 readout cycles with a readout time of 25.5 μs."

    In fact, when I analyzed the photon-counting histogram (PCH) shown in Fig 6 in this paper, I cannot obtain 0.18e- rms read noise, and instead consistently get about 0.23e- rms read noise. The authors draw just a peak and shoulders fit to obtain 0.18e- but this is generally inaccurate. I have used the VPM method (published in IEEE JEDS in May) and obtain 0.23e- rms. I have also done a full model fit to the entire PCH and also obtain 0.23e- rms. It is quite conclusive and anyone else can give it a try and see what you get using Fig. 6.


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