Speaker
Mr
Ondrej Sik
(postgradual student)
Description
Because direct band gap and high atom number, Cadmium Telluride based detectors are promissing for next generation of radiodiagnostic devices. In present manufacturing technology, the compensation of deep levels is not satisfactory solid. Presence of deep levels leeds to charge tramping in detectors bulk. The effect of charge tramping is inferior charge collection in contacts area and deteriorated spectral resolution of detector. Impacts of the all mentioned phenomena on detector properties increase with detector age. To describe this, the analysis of detector relaxation time, together with noise spectral density evaluation, is used in this paper.
For this purpose, we analyzed high-ohmic indium doped P type sample with gold contacts, prepared by chemical deposition of aqueous solution of AuCl3. The simulation of ageing process was carried by storing analyzed sample at temperature 100°C. After application of this process, the relaxation time of detector increased from order of hundreds seconds to 10^4 seconds. During the relaxation process, low frequency noise was observed. We found two stages of noise behaviour. Immediately after biasing, Noise spectrum has monotonous 1/fm behaviour with parameter m = 1.3 among the whole frequency range. At time 300 seconds after biasing, the decrease of detector resistivity became less abrupt. Another shape of ospectrum was observed. At low frequencies bellow 3Hz, the m parameter was 0.3 that is close to thermal noise behaviour. The rest of noise spectrum remained the same value of m = 1.3. During abrubt chage of detector current, after biasing, the magnitude of noise pectral density was 10^-7 V^2s. In time region more than 300 s after biasing, the magnitude of noise pectral density dropped to 10^-8 V^2s and remained constant for the rest of relaxation process that lasted for 10 000 seconds. From our measurements, we found that in first 300 seconds after biasing of aged sample, deep level filling by charge carriers takes important role in transport mechanism.
Author
Mr
Ondrej Sik
(postgradual student)
Co-authors
Dr
Alexey Andreev
(Scientist)
Dr
Belas Eduard
(Assoc. Professor)
Prof.
Josef Sikula
(Professor)
Prof.
Lubomir Grmela
(department CEO)
