E. Elad

Bio: E. Elad is an academic researcher from Oak Ridge National Laboratory. The author has contributed to research in topics: Ion implantation & Silicon. The author has an hindex of 4, co-authored 4 publications receiving 104 citations.

Drain Feedback - A Novel Feedback Technique for Low-Noise Cryogenic Preamplifiers

Abstract: This paper describes a novel technique of charge restoration - the drain feedback, based on the characteristics of the gate-to-drain junction of the input FET. The restoration charge required at the input of the preamplifier is generated by impact ionization in high-field regions of the FET. Actually the feedback is obtained by regulating the drain voltage according to the input energy count-rate product and consequently adjusting the electric field for the necessary charge generation. In the first part of the paper the principles of impact ionization in semiconductors at cryogenic temperatures are outlined and applied to junction FET's (JFET's) under saturation conditions. Then, the properties of FET gate leakage current generated by impact ionization are analyzed. Finally, the continuous mode of operation of the new feedback method is presented, and results from its application in x-ray spectroscopy with silicon and germanium detectors are given. Superior noise and count-rate performance coupled with simplicity and reliability are the outstanding features of the drain feedback method. It is the first feedback method in which the cryogenic input stage comprises the detector and the FET without the parasitic increases of stray capacitance or light-induced leakage currents characteristic of the other resistorless configurations.

Dead Layers in Charged-Particle Detectors

Abstract: This paper presents the results of dead-layer thickness measurements on silicon surface-barrier and ion-implanted detectors and a comparison of various methods for measuring dead-layer thicknesses. Our experimental arrangement and estimates of experimental error are discussed. Data on dead-layer thicknesses of n-type and p-type surface-barrier detectors and boron-implanted position-sensitive detectors are given. A linear relation was observed between the dead-layer thickness and the metal electrode thickness for both the rectifying and ohmic contact of barrier detectors. The thinnest dead layers measured were 270A (silicon equivalent) for 15 ?g/cm2 of gold and 460A (silicon equivalent) for 6 ?g/cm2 of aluminum.

Surface Barrier Structures with Various Metal Electrodes

Abstract: This paper describes the results of studies intended to provide a detailed understanding of the physical phenomena associated with dead layers sufficient to permit the production of rugged, reliable, ultrathin window detectors suitable for use in experiments which require the detection of very low energy radiation and also for the detection of heavily ionizing radiation, such as fission fragments. The properties of contacts formed by several different metals have been investigated. Interesting phenomena were observed when using nickel and chromium as the rectifying contact. The thinnest dead layers obtained so far are 270 A for gold, 280 A for aluminum, and 190 A for palladium, in terms of silicon-equivalence.

Low Temperature Characteristics of Ion Implanted Silicon Position Sensitive Detectors

Abstract: The operation of ion implanted silicon position sensitive detectors at low temperatures will be described. The improved noise performance of the detector at these temperatures in both the energy and position modes will be analyzed and its implications on low energy applications will be discussed. A large part of the investigation was devoted to the study of boron implanted resistors and their noise properties both at room temperature and cryogenic temperatures.

X-ray microanalysis with Si(Li) detectors

Abstract: SUMMARY The Si(Li) detector, with its relatively high collection solid angle, has brought X-ray microanalysis within the operating current limits of both SEMs and transmission microscopes. At present, the main deficiencies arise in the low-energy region of the spectrum, below about 2 keV. Here, detection efficiency falls off because of absorption in the entrance window, peaks invariably overlap and pile-up rejection is less effective. High-energy photons generated in transmission microscopes are responsible for new spectral artefacts and problems of overload. While computer processing of spectra can correct for most artefacts, background and peak overlaps, accuracy is fundamentally limited by counting statistics and the overall stability of the spectrometer. The technique will therefore benefit from improved design of both electronic circuitry and components. For example, advances in FET design may bring a substantial reduction in electronic noise which will not only improve resolution at low energies, but will also improve discrimination between small pulses and noise so that pile-up rejection can be more effective. This will be most important when a very thin entrance window is used to permit observation down to the C Kα energy (282 eV) although the hazards involved in such ‘windowless' operation still limit its application. The stability of detection efficiency with time has been exploited in methods which attempt to remove the need for repetitive standardization of the spectrometer and new techniques have been developed for the analysis of thin films, particles and rough surfaces which make use of information contained in the bremsstrahlung continuum.

Electronic noise in charge sensitive preamplifiers for X-ray spectroscopy and the benefits of a SiC input JFET

Abstract: A comprehensive summary and analysis of the electronic noise affecting the resolution of X-ray, γ-ray and particle counting spectroscopic systems which employ semiconductor detectors and charge sensitive preamplifiers is presented. The noise arising from the input transistor of the preamplifier and its contribution to the total noise is examined. A model for computing the noise arising from the front-end transistor is also presented and theoretical calculations comparing the noise contribution of transistors made of different materials are discussed, emphasizing the advantages of wide bandgap transistor technology.

Continuous charge restoration in semiconductor detectors by means of the gate-to-drain current of the integrated front-end JFET

Abstract: A continuous reset method for discharging the leakage current and the signal charge in semiconductor radiation detectors with on-chip electronics has been studied and experimentally verified. The charge collected at the output electrode of the detector is discharged by means of the gate-to-drain current of the front-end JFET integrated in the detector itself. The suitable value of gate current is reached by means of a "weak" avalanche breakdown mechanism which occurs in a high-field region of the transistor channel. When the JFET is operated in a source follower configuration, this mechanism is self-adapting to new values of leakage or signal currents.