Radiation hardness study of semi-insulating GaAs detectors against 5 MeV electrons

Abstract

A radiation hardness study of Semi-Insulating (SI) GaAs detectors against 5 MeV electrons is described in this paper. The influence of two parameters, the accumulative absorbed dose (from 1 to 200 kGy) and the applied dose rate (20, 40 or 80 kGy/h), on detector spectrometric properties were studied. The accumulative dose has influenced all evaluated spectrometric properties and also negatively affected the detector CCE (Charge Collection Efficiency). We have observed its systematic reduction from an initial 79% before irradiation down to about 51% at maximum dose of 200 kGy. Relative energy resolution was also influenced by electron irradiation. Its degradation was obvious in the range of doses from 24 up to a maximum dose of 200 kGy, where an increase from 19% up to 31% at 200 V reverse voltage was noticed. On the other hand, a global increase of detection efficiency with accumulative absorbed dose was observed for all samples. Concerning the actual detector degradation we can assume that the tested SI GaAs detectors will be able to operate up to a dose of 300 kGy at least, when irradiated by 5 MeV electrons. The second investigated parameter of irradiation, the dose rate of chosen ranges, did not greatly alter the spectrometric properties of studied detectors.

Radiation hardness limits in gamma spectrometry of semi-insulating GaAs detectors irradiated by 5 MeV electrons

“…Detectors investigated in this paper are the same samples as those studied and described in our previous papers [8][9][10][11][12]. The Schottky barrier detectors were made of a bulk VGF (Vertical Gradient Freeze) SI GaAs grade of 230 µm thickness with the circular Schottky electrode made of Ti/Pt/Au (10/35/90 nm) multilayer on the top and a whole area quasi-ohmic metal electrode from Ni/AuGe/Au (30/50/90 nm) multilayer on the back side of the substrate.…”

“…Si; GaAs detectors achieve higher detection efficiency of γ-and X-rays. There are only a few studies dealing with radiation resistance of GaAs detectors against high-energy electrons [6][7][8][9][10][11][12], however they present promising results. Afanaciev et al irradiated the Cr-doped GaAs sensors by 10 and 8.5 MeV electron beam at a dose rate of 20 to 400 kGy/h to a total dose of 1.5 MGy and observed the charge collection efficiency (CCE) degradation with the absorbed dose [6].…”

“…Torres et al irradiated Cr-doped GaAs detectors by 22 MeV electrons to doses in range from 48 to 1550 kGy with 50 to 500 kGy/h dose rates and they noticed an increase of dark current and deterioration in CCE with increasing cumulative dose [7]. We have also studied the spectrometric and electrical properties of developed SI GaAs detectors influenced by high energy electron irradiation, however, in lower range of doses, from 1 kGy up to 200 kGy and at dose rates from 20 to 80 kGy/h before [8][9][10][11][12]. In this paper we are continuing in our radiation hardness study of SI GaAs detectors against 5 MeV electrons with cumulative doses up to 1000 kGy.…”

Spreading of an active region of semi-insulating GaAs detectors after radiation degradation

“…Previous studies have shown the ability of GaAs detectors to withstand doses of a few MGy when degraded by MeV electrons with the main limiting factor which is the charge collection efficiency decreasing with overall dose [13][14][15][16][17][18]. On the other hand, we have observed an improvement of the detection efficiency after initial detector degradation by 5 MeV electrons up to doses of 200 kGy [13] when measuring both the gamma as well as the alpha particle spectra of 241 Am. This phenomenon was explained by an assumed expansion of the active detector volume.…”

“…In this paper we evaluate the alpha particle spectra of 241 Am measured with the same semiinsulating GaAs detectors described in [13] but degraded by 5 MeV electrons up to 2 MGy doses. The detection efficiency is evaluated by integrated counts in the peak of the measured spectra.…”