GaAs Schottky diodes, made on semi-insulating liquid encapsulated Czochrals
ki grown material with concentrations of acceptor dopants N-a varying from
10(14) to 10(17) cm(-3), were investigated as alpha particle detectors. The
charge collection efficiency (CCE) was found to decrease dramatically with
increasing N-a. Optical spectra in transmittance and reflectance were accu
rately measured to determine the concentrations of both neutral and ionised
EL2 defects as a function of N-a. The concentration of ionised EL2(+) cent
res was shown to increase with N-a, and to be quasi inversely proportional
to the CCE values. This behaviour strongly supports the hypothesis that the
EL2 defects play the main role in the compensation of the material and in
limitation of the detection properties.