The DEPFET detector-amplifier structure possesses several unique properties which make it extremely useful as readout element in semiconductor detectors and in particular as building block of semiconductor pixel detectors. Variations of DEPFETs can be tuned to specific requirements as to be sensitive only in predetermined time intervals, to measure signal charge with sub-electron precision, dead-time-free readout and with signal compression. These devices have been shown to work in simulations and in prototypes. Recently the first two fully developed detector systems have been finished and installed in the MIXS (Mercury Image X-ray Spectrometer) instrument of the Mercury Planetary Orbiter scheduled to be launched in 2017. A further DEPFET detector system under development is the DSSC (Depfet Sensor with Signal Compression) that will be installed in one of the beam-lines of XFEL. The requirements of the two projects are rather different. While the MIXS sensors are supposed to measure precisely the energy and position of single photons down to very low energies but at moderate rates, the DSSC has to measure the number of photons arriving in each pixel within a time interval of 220ns. Here the challenge is the capability of detecting single X-ray photons in one pixel simultaneously with up to 10,000 photons in some other pixels. Device functioning has been verified with sensors produced in a research laboratory. Now process and design have been adapted to an industrial type production line, allowing additional improvements.

Depleted field effect transistors (DEPFET) are used to achieve very low noise signal charge readout with sub-electron measurement precision. This is accomplished by repeatedly reading an identical charge, thereby suppressing not only the white serial noise but also the usually constant 1/f noise. 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.

Journal Article Setup and Practical Applications of a pnCCD Based XRF System Get access Jeffrey M Davis*, Jeffrey M Davis* PNDetector GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Julia Schmidt, Julia Schmidt PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Martin Huth, Martin Huth PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Sebastian Ihle, Sebastian Ihle PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Daniel Steigenhofer, Daniel Steigenhofer PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Peter Holl, Peter Holl PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Gerhard Lutz, Gerhard Lutz PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Udo Weber, Udo Weber PNDetector GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Adrian Niculae, Adrian Niculae PNDetector GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Heike Soltau, Heike Soltau PNDetector GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar ... Show more Lothar Striider Lothar Striider PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munchen, Germany Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 21, Issue S3, 1 August 2015, Pages 167–168, https://doi.org/10.1017/S1431927615001634 Published: 23 September 2015

Journal Article High Speed, High Throughput Two Dimensional Direct Electron Detector Based on the Concept of pnCCDs Get access L Strüder, L Strüder PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar J Soltau, J Soltau PNDetector GmbH, Emil-Nolde-Str. 10, 81735 München, Germany Search for other works by this author on: Oxford Academic Google Scholar J Schmidt, J Schmidt PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar R Hartmann, R Hartmann PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar M Huth, M Huth PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar H Soltau, H Soltau PNDetector GmbH, Emil-Nolde-Str. 10, 81735 München, Germany Search for other works by this author on: Oxford Academic Google Scholar P Holl, P Holl PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar M Simson, M Simson PNDetector GmbH, Emil-Nolde-Str. 10, 81735 München, Germany Search for other works by this author on: Oxford Academic Google Scholar G Lutz, G Lutz PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar H Ryll H Ryll PNSensor GmbH, 80803 München, Römerstr. 28, Germany Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 20, Issue S3, 1 August 2014, Pages 392–393, https://doi.org/10.1017/S1431927614003687 Published: 27 August 2014

The DSSC (DEPFET Sensor with Signal Compression) is a new instrument with non-linear compression of the input signal in the sensor and with parallel signal processing (filtering, linear amplification, and digitization) for all pixels. The design goal is to achieve at the same time single photon detection and high dynamic range, both for photon energies down to 0.5 keV and read-out speeds up to 4.5 MHz. Realization of this goal requires an accurate calibration of the non-linear system gain (NLSG), i.e. of the non-linear dependence of the digital DSSC output signal on the input signal charge generated by incident photons, over the full dynamic range of the detector. We present an overview of our basic strategy for calibrating the NLSG. The feasibility of our calibration strategy is demonstrated using our system simulation package, which is briefly described. Finally, we demonstrate the DSSC capabilities by simulating the measurement of a T4 virus diffraction image as recorded at the Linac Coherent Light Source.

A new DEPFET detector-amplifier structure with strongly non-linear characteristics is presented. It will be used as basic element of an X-ray pixel detector at the new XFEL free electron laser radiation source to be constructed in Hamburg, Germany, providing at the same time single X-ray photon detection and high dynamic range even when operated at readout frequency up to 5MHz. This is possible due to the new detector concept that adds to the excellent DEPFET properties – combined function of detector amplifier and data storage, full sensitivity over whole bulk, non-destructive readout, low serial noise and absence of reset noise – the new features of very large charge handling capability and signal compression. Concept and design will be presented and properties demonstrated by extended computer simulations.

An experiment was performed to measure the current related damage rate of silicon soon after a 10 MeV proton irradiation at −50° C, in a condition in which the effect of the leakage current annealing is negligible. This measurement is fundamental to predict the spectroscopic performance of the macropixel detectors which will be mounted on the Simbol-X and BepiColombo space missions. Macropixel detectors consist on matrices of Silicon Drift Detectors with an integrated DEPFET readout node on each pixel and offer an optimal solution when a large pixel area is needed but the noise should be kept at levels allowing X-ray spectroscopy. The most critical aspect of the operation of these detectors, in particular of the one which will be used in the BepiColombo mission, is whether the leakage current increase due to the proton irradiation would still allow the required energy resolution. This leakage current increase cannot be predicted with the available models because, during the whole mission, the sensor will be kept at temperatures below −40° C, and the existing empirical parameterizations are valid only at higher annealing temperatures. The irradiation was performed with diodes at the tandem accelerator of the Meier-Leibnitz Laboratorium in Garching with 10-MeV protons and fluences below 1011 protons/cm2, the interesting range for the missions. The diodes were cooled at a temperature of −50° C during the experiment and biased and read out with a charge sensitive preamplifier to perform a dosimetry based on proton counting. The leakage current was measured at the end of every exposure, before warming up and replacing the samples. Its time evolution after several steps of annealing at 60° C was then studied in the laboratory to check the agreement with the NIEL hypothesis predictions and thus, to validate the experiment. The experimental setup, the measurements of current induced damage rate at- - −50° C and its annealing are discussed in detail. The consequences on the Simbol-X and BepiColombo experiments are also examined.

We propose a new detector system capable to fulfil the requirements of the future XFEL in Hamburg. The instrument will be able to record X-ray images with a maximum frame rate of 5MHz and to achieve a high dynamic range. The system is based on a pixel-silicon sensor with a new designed non-linear-DEPFET as a central amplifier structure. The detector chip is bump-bonded to a set of mixed signal readout ASICs that provide full parallel readout. The signals coming from the detector, after having been processed by an analog filter, are immediately digitized by a series of 8-ENOB ADCs and locally stored in a custom designed memory also integrated in the ASICs designed in the 130nm CMOS technology. During the time gap of 99ms of the XFEL machine, the digital data are sent off the focal plane to a DAQ electronics that acts as an interface to the back-end of the whole instrument. The pixel sensor has been designed so as to combine high energy resolution at low signal charge with high dynamic range. This has been motivated by the desire to be able to be sensitive to single low energy photons and, at the same time, to measure at other positions of the detector signals corresponding to up to 104 photons of 1keV. In order to fit this dynamic range into a reasonable output signal swing, achieving at the same time single photon resolution, a strongly non linear characteristics is required. The new proposed DEPFET provides the required dynamic range compression at the sensor level, considerably facilitating the task of the electronics. At the same time the DEPFET charge handling capacitance is enormously increased with respect to standard DEPFETs. The Pixel matrix will have a format of 1024×1024 with a pixel size of 200×200 µm2.

The need of high quality spectroscopic semiconductor imaging detectors in X-ray astronomy was the principal driving force in founding the MPI Semiconductor Laboratory. Detectors developed in this laboratory are based on new function principles and are processed in the silicon detector processing line established within the laboratory. We describe the development of pnCCDs as already used in the XMM-Newton European X-ray observatory and foreseen for eROSITA, the DEPFET based pixel detector for XEUS and a new development which makes it possible to measure charge with a precision below one elementary charge. A noise value of 0.25 electron r.m.s. has already been reached.

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.

DEPMOSFET based Active Pixel Sensor (APS) matrices are a new detector concept for X-ray imaging spectroscopy missions. They can cope with the challenging requirements of the XEUS Wide Field Imager and combine excellent energy resolution, high speed readout and low power consumption with the attractive feature of random accessibility of pixels. From the evaluation of first prototypes, new concepts have been developed to overcome the minor drawbacks and problems encountered for the older devices. The new devices will have a pixel size of 75 μm × 75 μm. Besides 64 × 64 pixel arrays, prototypes with a sizes of 256 × 256 pixels and 128 × 512 pixels and an active area of about 3.6 cm2 will be produced, a milestone on the way towards the fully grown XEUS WFI device. The production of these improved devices is currently on the way. At the same time, the development of the next generation of front-end electronics has been started, which will permit to operate the sensor devices with the readout speed required by XEUS. Here, a summary of the DEPFET capabilities, the concept of the sensors of the next generation and the new front-end electronics will be given. Additionally, prospects of new device developments using the DEPFET as a sensitive element are shown, e.g. so-called RNDR-pixels, which feature repetitive non-destructive readout to lower the readout noise below the 1 e- ENC limit.

In this work we demonstrate theoretically and experimentally the capability to reduce the readout noise of an optical and X-ray photon detector based on the semiconductor DEPFET device below a level of only 0.3e- ENC (equivalent noise charge). The readout method used is called "Repetitive Non Destructive Readout" (RNDR) and was realised by placing two single DEPFET-devices next to each other and by coupling their charge storing region by an additional gate. By transferring the stored charge from one DEPFET to the other and vice versa the same charge can be measured non-destructively and arbitrarily often. Taking the average value of a large number n of these measurements, the noise is reduced by 1/radicn. The main advantage of such a detector is to greatly reduce the influence of the 1/f noise to the readout noise. The theoretically and experimentally achievable resolution for different operating parameters (leakage current, readout noise, number and duration of readouts) was investigated by Monte-Carlo simulations and verified on a real RNDR minimatrix (pixelarray). Single optical photon detection with high quantum efficiency and, even more fascinating, the possibility to distinguish between different numbers of photons e.g. 100 from 101 is presented in measurements.

Starting from the basic photon detection process in semiconductors, the function, principles and properties of sophisticated silicon detectors are discussed. These detectors are based on, or inspired by, the semiconductor drift detector. They have already shown their potential in X-ray astronomy ( pnCCD) and in X-ray spectroscopy ( silicon drift diode), and further detector types ( DEPFET pixel detector and macro-pixel detector) are under development for several other future experiments. The detectors seem to be very well suited for synchrotron radiation experiments.

A new concept for a silicon single photon counter has been developed at the Semiconductor Laboratory of the Max-Planck-Institute for Physics. The concept combines the principles of a drift diode and an avalanche diode. The electron which is generated by an incoming photon has to drift to the small avalanche region and avalanche breakdown will take place. The detector is operated in Geiger mode. In order to provide high efficiency and good timing properties, the electrons have to be focussed properly with short time jitter. Therefore, drift and timing properties have been investigated using simulations.

A new avalanche detector concept is presented that promises very high (close to 100%) quantum efficiency. Integrating the structure into the centre of a drift diode one obtains a large area device that focuses the photoelectron onto a small “point-like” avalanche region. Such a device can be used as building block for a “silicon photomultiplier”. Implementing the structure into the output node of a pnCCD a pixel detector sensitive to single optical photons can be constructed.

Recently a new type of photodetector was introduced; the so-called Silicon PhotoMultiplier (SiPM). Its good characteristics make SiPM suitable for many applications. Yet, for low light level applications higher quantum efficiency is required. A new detector concept is presented that promises very high (close to 100%) quantum efficiency in a wide wavelength range.

The DEPFET device concept offers unique properties that make it useful for applications in X-ray astronomy and particle physics as well as in other fields. They form the basis for two major projects of the MPI Semiconductor Laboratory. This survey reviews device concepts, potential, technology and properties of devices produced at the laboratory. A self-aligning double poly double metal technology has been developed and already the first prototype production run has delivered devices with excellent properties (for example, a noise of ENC=2.2 electrons at room temperature). Another new technology allows the production of very thin (50 μm) detectors.