Temperature dependence of the avalanche multiplication process and the impact ionization coefficients in Al0.8Ga0.2As

Direct detection of Tritium and Carbon-14 beta particles with GaAs photodiodes

“…Consequently, the main driver limiting the efficiency of the detectors for 3 H beta detection is the dead overlayer, rather than the relative thinness of the active region. However, at 156.48 keV, the 14 C endpoint energy, shown in figure 3, the energy deposition extends well into the substrate of the detectors, showing, as expected, that the thinness of the detectors reduces the efficiency at higher energies. The detectors' efficiencies and charge deposition are planned to be more extensively explored in future using software of our own creation and GEANT4 [45] so that the detailed spectral response of the detectors to β − radiation can be predicted from computer modelling.…”

“…The diodes were individually connected to a custom-made low-noise charge-sensitive preamplifier, which was connected to an Ortec 571 shaping amplifier (shaping time = 3 µs) and an Ortec EASY-MCA-8k multi-channel analyser (MCA). To illuminate the detector, 3 H and 14 C β − particle sources were prepared by placing 1 µl 37 kBq specific activity drops of 14 C-choline and a 3 H-drug compound used for labelling samples in the biological sciences onto nitrocellulose. After drying, and in turn, each 37 kBq source was then positioned as close as possible (∼ 1 mm) to the detector without disturbing the bond wires connecting the diodes to the packaging.…”

“…All spectra were accumulated at room temperature (∼ 20 ˚C). The gain of the shaping amplifier was reduced by a factor of 4.15 for the 14 C spectrum so that β − particles with energy equal to the 14 C endpoint were still within the range of the MCA. The 3 H spectrum was calibrated using the zero energy noise peak from the preamplifier and the endpoint energy of the source.…”

“…The 3 H spectrum was calibrated using the zero energy noise peak from the preamplifier and the endpoint energy of the source. It was not possible to calibrate the 14 C spectrum using the 14 C endpoint, because the detector active region is thin and β − particles with energy = 156.48 keV are predominantly not absorbed in the active region of the detector (see figure 3). Therefore, the 14 C spectrum was energy calibrated using the 3 H endpoint and the measured difference in gain between the two set-ups.…”

Temperature dependence of the average electron-hole pair creation energy in Al0.8Ga0.2As

“…The temperature dependence is reported over the range of 261 K-342 K and is found to be best represented by the equation e AlGaAs ¼ 7.327-0.0077 T, where e AlGaAs is the average electron-hole pair creation energy in eV and T is the temperature in K. The compound semiconductor Al 0.8 Ga 0.2 As has received attention as a detector material for use in soft X-ray spectroscopy instruments which need to operate at high temperature ()20 C). [1][2][3][4][5][6][7][8][9][10][11][12][13] At high temperatures, the wide bandgap of Al 0.8 Ga 0.2 As (2.09 eV (Ref. 14)) leads to a thermally generated leakage current lower than that which would be present in a silicon detector of the same design.…”