Semiconductor Drift Detectors Research Articles

Anode capacitance measurement of silicon drift detectors in operating conditions

We describe a technique for measuring with high accuracy and precision the capacitance of the anode of a semiconductor drift detector (SDD) fully biased in operating conditions and connected to the front-end electronics. The proposed method does not require the use of a probe station, making it suitable for low-cost and easy-to-setup application environments. We have performed measurements on four SDDs with different geometries and production processes, observing a total capacitance ranging from 20 fF to 75 fF, depending on the bias conditions. Different components of the anode capacitance with respect to the front cathode and the adjacent drift cathodes have been measured and commented as well. Precision in the capacitance measurements better than 0.1 fF has been obtained. These results can be effectively used for the optimization of the front-end electronics for SDDs to achieve minimum electronic noise.

Analytical Model of the Discharge Transient in Pulsed-Reset Charge-Sensitive Amplifiers

A study of the reset transient of charge-sensitive amplifiers operating with a pulsed switch in parallel to the feedback capacitance is presented. Analytical models have been developed for amplifiers in both linear and slew rate regimes during the reset phase. The models predict the time interval required to reset the amplifier that, in most cases, significantly differs by the simple discharge of the feedback capacitance through the switch resistance and strongly depends on the open-loop gain and bandwidth of the core amplifier and on the input capacitance. The models also quantitatively predict spurious voltage transients at the preamplifier's input and possible ringings at the output, as a function of the main general parameters of the circuit. A case application study of the presented model is proposed for low-capacitance detectors, such as semiconductor drift detectors or small pixel detectors.

Readout ASICs for silicon drift detectors

Semiconductor drift detectors (SDDs) are widely used in X-ray spectroscopy due to their excellent performances in terms of energy resolution and detection-rate. Suitable low noise readout electronics have to be designed in order to exploit the SDD intrinsic performances. The integration of this electronics in custom application specific integrated circuits (ASICs) is mandatory when the compactness of the detection system (detector and electronics) and the need to read out multi-elements SDDs are primary requirements. This work describes the development of three circuits for SDDs, which are a charge sensitive preamplifier operating in the pulsed reset regime, a fast shaping amplifier for high-count rates applications and a multi-channel ASIC that provides the whole analog processing and multiplexing of the signals from SDD arrays. The ASICs have been tested with SDDs with on-chip JFET and the results are presented here.

Semiconductor drift detectors for X- and gamma-ray spectroscopy and imaging

The semiconductor drift detectors (SDDs) show basic advantages, in terms of spectroscopic resolution and detection rate, with respect to other semiconductor detectors. These advantages are strictly related to the very low values of the output capacitance of these devices. In this paper the working principles and the performance of the SDDs are presented and the most recent devices (“droplet type” SDDs and monolithic arrays of SDDs) are introduced. The requirements of front-end electronics for the readout of the SDDs signals are then discussed and the most recent implementations (pulsed-reset preamplifiers, multi-channel ASIC readout circuits) are introduced. Some relevant applications of SDDs in the field of X-ray spectroscopy for material analysis and for nuclear physics experiments, and in the field of gamma-ray imaging, are presented as a conclusion.

Effect of Charge Recombination on Amplitude and Time Measurement of Induced Signals in Semiconductor Drift Detectors

The effect of charge recombination on the noise associated with the signal current at the anode of a semiconductor drift detector is studied for both time and amplitude measurements. The analysis is performed by fully taking into account the diffusion of electrons in the semiconductor, the electrostatic induction process that gives rise to the signal, and the correct boundary condition at the anode for the electron density. Both the time variance and the amplitude noise-to-signal ratio are calculated as a function of the filter width for different values of the time constant of the recombination process. A comparison with previous results based on more simplified treatments is also given.

Performance Evaluation of an Advanced XRF Elemental Mapping System Featuring a Novel Ring-Shaped Monolithic Array of Silicon Drift Detectors

This paper introduces an ultra-fast X-ray fluorescence (XRF) spectrometer based on a novel ring-shaped semiconductor drift detector (SDD) and on a novel readout and processing electronics and discusses its performance. The new detector is based on 4 independent droplet type SDDs monolithically integrated on the same chip. The detector shape optimizes the collection angle of the fluorescence radiation. The X-ray excitation beam is focused on the sample by means of a polycapillary lens through the hole cut in the center of the detector. The droplet type SDD is characterized by a better energy resolution and a better peak-to-valley ratio with respect to the ones of conventional SDDs. The energy resolution is of the order of 140 eV FWHM on the Mn Kalpha line with 1 mus shaping time at -15degC and the peak-to-valley ratio is of the order of 6000. In order to fully exploit the detection rate performance of this detector we have developed a novel read-out electronic unit with selectable shaping time and on-board histogramming capability.

Silicon drift and pixel devices for X-ray imaging and spectroscopy

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 (pn-CCD) 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.

Review of semiconductor drift detectors

A short review of semiconductor drift detectors is given. The emphasis is given to detectors intended for tracking of fast charged particles for experiments in particle physics and high energy heavy-ion physics. The use and performance of this kind of detector in past, present and future experiments is described together with the experience learned during the design, production and data taking phases.

Noise of the induced signal pulses in semiconductor drift detectors

The noise associated with the signal current at the anode of a semiconductor drift detector is evaluated when the electrostatic induction giving rise to the signal is fully taken into account and the correct boundary condition at the anode for the electron density is considered. The consequent signal-to-noise ratio for both time and amplitude measurements is calculated as a function of the filter width and compared with previous results based on more simplified treatments.

Multichannel implementation of ROTOR amplifier for the readout of silicon drift detectors arrays

In this paper, we present a multichannel very large scale integration implementation of ROTOR, a time-variant parameters shaping amplifier designed for the readout of high-rate asynchronous signals from multi-element solid-state X-ray detection systems. In particular, ROTOR was optimized for high-rate X-ray spectroscopy with multi-element semiconductor drift detectors (SDDs) in applications using synchrotron light sources such as X-ray holography or extended X-ray absorption fine structure (EXAFS) experiments. A 30 channels circuit has been implemented in the 1 /spl mu/m/5 V JFET/CMOS technology of the Fraunhofer-Institut, Duisburg, Germany. Each analog channel features a trapezoidal weighting function, 1.6 /spl mu/s wide, obtained by means of a switched-current technique. A digital section, directly integrated on the ROTOR chip, allows the timing and control of all the analog switches of the amplifiers as required for the circuit functionality, without the need of external signals. The main features of the circuit design and the results obtained in the experimental characterization of the prototype, also in spectroscopy measurements by using an SDD, are presented.

Semiconductor drift detectors: applications and new devices

Recent technological developments and new topology designs have made semiconductor drift detectors ideal devices for high-resolution x-ray spectrometry. In this paper the basic topology of a semiconductor drift detector with on-chip electronics specially designed for x-ray spectrometry is reviewed. These devices have been used for the first time in x-ray and γ-ray spectroscopy applications. In particular, the results obtained in non-destructive analyses by using a EDXRF spectrometer based on a Peltier cooled semiconductor drift detector and in photodetection of scintillation light are reported. The working principle and the first experimental results for a novel position-sensitive x-ray detector with spectroscopic capability are presented. Copyright © 1999 John Wiley & Sons, Ltd.

Semiconductor drift detectors: applications and new devices

Semiconductor drift detectors: applications and new devices

Determination of the interaction coordinate in drift detectors through the timing of induced signals

The time centroid of the current pulse induced at the anode of a semiconductor drift detector is calculated as a function of the interaction coordinate for arbitrary drifting fields. The effects of its behavior on the determination of the absolute position of the interaction point are studied. For a typical bias condition of the detector, the paper shows that an error up to few hundred micrometers is made in the position reconstruction of the event if the described effects of the induction are not taken into account. The paper also shows that the time shift due to the perturbation of the drifting field caused by the discreteness of the field electrodes, is only of less than 1 ns, and therefore negligible in most applications.

Semiconductor drift detectors for high resolution X-ray spectroscopy

The properties and performances of silicon drift detectors for X-ray spectroscopy applications are presented. The peculiar characteristic of these detectors is the transport along the detector of the charge generated by the radiation toward a small collecting anode, whose capacitance can be as low as 60 fF, irrespective of the sensitive area. This feature is the key of the extremely high resolution available from this class of devices. Recent experimental results showing an energy resolution at room temperature down to 110 electrons rms with a detector of 1 cm 2 active area and external electronics are reported. Detectors with different topologies especially designed to improve the resolution in the X-ray energy range are presented. The status of the activity on direct integration of the electronics in the detector itself is also reported.

Double particle resolution in semiconductor drift detectors

The optimum signal processing of two close pulses produced by ionization of two close fast particles in a semiconductor drift detector is presented. The optimum is relative to the determination of charges produced by each particle and the average drift times for the released charges to reach the anode. The resolution of the charge and the drift time measurements in the presence of additive and nonadditive noises have been theoretically studied as functions of the distance between two fast ionizing particles and the amount of ionization produced by individual particles. Is it shown that the precision of the position determination of the individual particles remains good enough also in the case of a significant overlap of the two pulses.

Progress in semiconductor drift detectors

Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.