S.P. Beaumont

GaAs solid state detectors for particle physics

Abstract We report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionising particles. The radiation hardness and potential speed of simple diodes is shown to be more than competitive with silicon detector. A discussion is given of the present understanding of the charge transport mechanism in the detectors since it influences their charge collection efficiency. Early results from microstrip detectors are also described.

Charge transport properties of undoped SI LEC GaAs solid-state detectors

Abstract The GaAs detectors for minimum ionizing particles fabricated with commercial undoped SI GaAs show good quality as minimum ionizing particle detectors. A discussion is given of the present understanding of the charge transport mechanism in the detectors since it influences their charge collection efficiency.

Gallium arsenide microstrip detectors for charged particles

Microstrip detectors have been constructed from gallium arsenide (GaAs) wafers made from undoped LEC (liquid-encapsulated Czochralski) semi-insulating substrate material. Tests were performed using minimum ionising particles to ascertain their properties as charged particle detectors. The results show that the devices work wellm, with good signal-to-noise ratio (typically 7). The effects of gamma ray and neutron irradiation have been studied and shown to be small up to levels exceeding 20 Mrad and 1014 n/cm2, respectively.

Gallium arsenide charged particle detectors; trapping effects

The progress on the development of gallium arsenide particle detectors is reviewed. The limitation to the performance is the presence of traps. Studies of the trap properties using α particle DLTS measurements and C-V measurements are described.

First results from GaAs double-sided detectors

Abstract Preliminary results are presented on the performance of double-sided microstrip detectors using Schottky contacts on both sides of a semi-insulating (SI) GaAs substrate wafer, after exposure to 1014 neutrons cm−2 at the ISIS facility. A qualitative explanation of the device behaviour is given.

LEC SI-GaAs detectors for gamma rays

Abstract Detectors with a p-i-n structure based on Liquid Encapsulated Czochralski (LEC) grown Semi-Insulating (SI) GaAs have been fabricated. The current-voltage ( I – V ) characteristics and their response to γ-rays have been studied. Measurements of the peak charge collection efficiency (cce) have been compared with a model assuming a uniform electric field. The comparison indicates that this field is not uniform. The peak cce at 500 V is found to be 52% and 82% in 400 μm and 200 μm thick detectors respectively. The resolution of the 57 Co full energy peak is between 10% and 13% at 400 V.

GaAs solid state detectors for physics at the LHC

The authors report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionizing particles. The radiation hardness and potential speed of simple diodes are shown to be more than competitive with silicon detectors. A discussion is given of the present understanding of the charge transport mechanism in the detectors as it influences their charge collection efficiency. Early results from microstrip detectors which are relevant for high radiation regions of Large Hadron Collider (LHC) detectors near the beam pipe and in the forward region are also described. The authors have established the ability of GaAs Schottky diode detectors to tolerate radiation loads at the level expected in more than one year of running at a radial distance of only a few cm from the intersection point of the proposed LHC collider at nominal luminosity. The diode output signal of only a few nanoseconds is very satisfactory for the new colliders.<<ETX>>

GaAs solid state detectors for high energy physics

Progress in the development of detectors based on semi-insulating GaAs for experiments at future hadron colliders is presented. Effects of neutron and gamma irradiation at the levels of 10[sup 14] ncm[sup [minus]2] and 20 MRad respectively, have been shown to be small. Testbeam studies have shown that microstrip detectors can detect minimum ionizing particles with a good signal to noise ratio despite having low charge collection efficiencies. The problem of charge loss in the detectors is now better understood and new detectors have shown improved charge collection efficiencies.

Gallium arsenide microstrip detector and pixel detector developments

Recent developments in improved charge collection efficiency of GaAs pad detectors are described together with their radiation hardness to irradiation by neutron, proton and pions. While the resistance to neutron irradiation is satisfactory more susceptibility is found to charge particle irradiation. Test beam results from microstrip detectors tested in a 70 GeV pion beam at CERN are also presented. Progress with GaAs pixel detectors is also reported.

GaAs Detectors for Physics at the LHC

Over the last two years the Glasgow and CERN-based LAA groups have successfully constructed GaAs detectors for minimum ionising particles with radiation hardness and potential speed which is more than competitive with silicon detectors. The timely development of this new technology, in particular for high radiation regions of LHC detectors near the beam pipe and in the forward region, now requires the investment of more resources and more intensive effort, including industrial collaboration in detector fabrication. In addition, there is an urgent need for the development of appropriate read-out electronics with radiation tolerance and speed characteristics to match the detectors, and with the lowest possible power consumption, needed for the large number of channels required in a vertex detector, for example. The present report describes the results obtained using GaAs Schottky diode detectors which we have constructed, and the initial steps which we have taken towards the design of a GaAs preamplifier to match the detectors.