M. Trimpl

Design and technology of DEPFET pixel sensors for linear collider applications

The performance requirements of vertex detectors for future linear collider experiments is very challenging especially for the detectors innermost sensor layers. The DEPleted Field Effect Transistor (DEPFET) combining detector and amplifier operation is capable to meet these requirements. A silicon technology is presented which allows production of large sensor arrays consisting of linear DEPFET detector structures. The envisaged pixel array offers a low noise and low power operation. To ensure a high radiation length a thinning technology based on direct wafer bonding is proposed.

A fast readout using switched current techniques for a DEPFET-pixel vertex detector at TESLA

A fully depleted silicon detector with a first amplifying transistor integrated in every pixel (DEPFET) is a promising proposal for the pixel-based vertex detector at TESLA. The DEPFET offers good spatial resolution, an excellent signalto-noise ratio and low power consumption in a row-wise operation mode. A readout concept for a DEPFET pixel array matching the requirements at TESLA is described. In order to meet the operation specifications at TESLA (50 MHz row rate), a readout architecture based on current mode techniques (Switched Current) is presented. It contains stand alone zero suppression offering a triggerless operation. The core of the readout chip, a fast operating current memory cell, is discussed in detail. The results of a first prototype chip, CURO I (CUrrent ReadOut), show that the requirements for TESLA are achievable. r 2003 Elsevier B.V. All rights reserved.

Spectroscopic and imaging performance of DEPFET pixel sensors

Abstract DEPFET pixel sensors consist of a p-channel JFET directly integrated into a high-ohmic n-silicon substrate. They offer a very low-noise performance at room temperature and are therefore of interest for applications in biomedicine, X-ray astronomy and particle physics. Measurements on single pixel devices demonstrating the low-noise potential of DEPFET sensors are shown. The DEPFET pixel bioscope system is based on a 64×64 matrix of DEPFET pixels. Measurements of the homogeneity of the charge collection efficiency and of the spatial resolution of the system as well as on the capability of DEPFET sensors to detect tritium with a good efficiency are presented.

Readout concepts for DEPFET pixel arrays

Field effect transistors embedded into a depleted silicon bulk (DEPFETs) can be used as the first amplifying element for the detection of small signal charges deposited in the bulk by ionizing particles, X-ray photons or visible light. Very good noise performance at room temperature due to the low capacitance of the collecting electrode has been demonstrated. Regular two-dimensional arrangements of DEPFETs can be read out by turning on individual rows and reading currents or voltages in the columns. Such arrangements allow the fast, low-power readout of larger arrays with the possibility of random access to selected pixels. In this paper, different readout concepts are discussed as they are required for arrays with incomplete or complete clear and for readout at the source or the drain. Examples of VLSI chips for the steering of the gate and clear rows and for reading out the columns are presented.

First results of DEPFET based Active Pixel Sensor prototypes for the XEUS Wide Field Imager

The concept of an Active Pixel Sensor (APS) based on the integrated detector/amplifier structure DEPFET (DEpleted P-channel Field Effect Transistor) has been developed to cope with the challenging requirements of the XEUS Wide Field Imager. The DEPFET-APS combines high energy resolution, fast readout, and random accessible pixels allowing the application of flexible readout modes. First prototypes of DEPFET-based Active Pixel Sensors with a 64 x 64 pixel format and 75 μm x 75 μm pixel area have been produced at the MPI semiconductor laboratory. The APS is read out row by row, i.e. the pixel signals of one row are processed in parallel by a 64 channel CMOS amplifier/multiplexer chip of the CAMEX type. The addressing of one row of pixels for readout and reset is done by two control chips of the SWITCHER type fabricated in a high-voltage CMOS technology. The processing time for one row is of the order of a few micro-seconds. APS operation, the control and data acquisition system are described, and first experimental results are presented.

DEPFET - a pixel device with integrated amplification

In the DEPFET pixel concept, the absorbed radiation directly modulates the channel current of a p-JFET transistor being integrated into a fully depleted high ohmic silicon substrate in every pixel cell, offering very low noise operation at room temperature. Hence, DEPFET pixels open new possibilities in biomedical applications, but also have a potential in particle physics and astrophysics. Second prototype 50 mm � 50 mm single pixels as well as large ð64 � 64Þ DEPFET matrices have been successfully produced and operated confirming the low noise behavior ð12eÞ: Device studies as well as a full DEPFET pixel Bioscope system to be used in real-time digital autoradiography with excellent spatial and energy resolution for X-rays are presented. r 2002 Elsevier Science B.V. All rights reserved.

A DEPFET pixel Bioscope for the use in autoradiography

Abstract The DEPFET structure consists of a field effect transistor integrated on high-resistivity silicon, which can be used as a radiation detector. Due to several features (e.g. very low noise at room temperature, information storage capability and a thin, homogeneous entrance window), the DEPFET concept is useful for various applications. In order to apply a DEPFET pixel detector in autoradiography, 64×64 matrices with a pixel size of 50 μm ×50 μm were built. Using several ASIC chips for the readout control and signal processing, a complete sensor system allows a row-by-row detector readout with almost continuous sensitivity. First results on the device homogenity, the quantum efficiency and the very promising noise performance are presented.

Development of a prototype module for a DEPFET pixel vertex detector for a linear collider

For operation at a linear collider the excellent noise performance of depleted field effect transistor (DEPFET) pixels allows building very thin detectors with high spatial resolution and low power consumption. However, high readout speeds of 50 MHz line rate and 20 kHz for the full detector must be reached. A prototype system is presented, using a new DEPFET pixel matrix (128 /spl times/ 64 pixels), fast steering chips (Switcher II) for row wise operation and a fast current based readout chip (CURO II). The sensors with small linear DEPFET pixels (22/spl times/36 /spl mu/m/sup 2/) are optimized for fast readout and high spatial resolution. Measurements show that the complete removal of the accumulated signal charge from the internal gate (complete clear), which is fundamental for the foreseen readout mode, is feasible. The current based readout chip CUROII, containing current memory cells, pedestal subtraction and on chip zero suppression for a triggerless operation has been fabricated and tested. First results of a full prototype system are presented.

Performance of a DEPFET prototype module for the ILC vertex detector

For the detection of secondary vertices of long lived bottom and charm quarks at the proposed International Linear Collider (ILC) a DEPFET pixel detector is one of the favored technology options. DEPFET pixel sensors, in which the amplifying transistor structure is contained in the pixel cell itself on a fully depleted bulk, are unique devices in terms of their large signal and low noise capability and their obtainable spatial resolution with very thin detectors. DEPFET pixel prototype modules with close to ILC specifications have been tested in the laboratory and, for the first time, in a 6 GeV electron test beam. The different noise sources have been calculated and compared with the measured value of ENC/spl ap/225 e/sup -/ for the entire readout chain.

Noise and spectroscopic performance of DEPMOSFET matrix devices for XEUS

DEPMOSFET based Active Pixel Sensor (APS) matrix devices, originally developed to cope with the challenging requirements of the XEUS Wide Field Imager, have proven to be a promising new imager concept for a variety of future X-ray imaging and spectroscopy missions like Simbol-X. The devices combine excellent energy resolution, high speed readout and low power consumption with the attractive feature of random accessibility of pixels. A production of sensor prototypes with 64 x 64 pixels with a size of 75 μm x 75 μm each has recently been finished at the MPI semiconductor laboratory in Munich. The devices are built for row-wise readout and require dedicated control and signal processing electronics of the CAMEX type, which is integrated together with the sensor onto a readout hybrid. A number of hybrids incorporating the most promising sensor design variants has been built, and their performance has been studied in detail. A spectroscopic resolution of 131 eV has been measured, the readout noise is as low as 3.5 e- ENC. Here, the dependence of readout noise and spectroscopic resolution on the device temperature is presented.