NIEL DOSE DEPENDANCE FOR SOLAR CELLS IRRADIATED WITH ELECTRONS AND PROTONS
C. Baur1 , M. Gervasi2,3 , P. Nieminen1 , S. Pensotti2,3 , P.G. Rancoita2 and M. Tacconi2,3
1 ESA, ESTEC, AG Noordwijk, Netherlands
2 Istituto Nazionale di Fisica Nucleare, INFN Milano-Bicocca, Milano (Italy)
3 Department of Physics, University of Milano Bicocca, Milano (Italy)
The investigation of solar cells degradation and prediction of its end-of-life is of primary importance in the preparation of a space mission. In the present work, we investigate the reduction of solar-cells maximum-power resulting from irradiations with electrons and protons. Both GaAs single junction and GaInP/GaAs/Ge triple junction solar cells were studied. The results obtained indicate how i) the dominant radiation damaging mechanism is that due to atomic displacements, ii) the relative maximum power degradation is almost independent of the type of incoming particle, i.e., iii) to a first approximation, the fitted semi-empirical function expressing the decrease of maximum power depends only on the absorbed NIEL dose, and iv) the actual displacement threshold energy value (Ed = 21 eV) accounts for annealing treatments, mostly due to self-annealing induced effects. Thus, for a given type of solar cell, a unique power-maximum degradation curve can be determined as a function of the absorbed NIEL dose. The latter expression allows one to predict the performance of those solar cells in space radiation environment.
(Nucl. Instr. and Neth. in Phys. Res. B 2003)
D. Codegonia , A. Colderb , N. Croitorua,c , P. D’Angeloa , M. DeMarchia,d , G. Fallicae , A. Favallia , S. Leonardie ,M. Levaloisb , P. Marieb , R. Modicae , P. G. Rancoitaa and A. Seidmana,c
a INFN - Istituto Nazionale di Fisica Nucleare, Milan, Italy.
b Lermat, Caen, France.
c Department of Physical Electronics, Tel-Aviv University, Ramat Aviv, Israel.
d present address: Laben, Milano, Italy.
e STMicroelectronics, Catania, Italy.
In this paper experimental results on radiation effects on a BICMOS high speed commercial technology, manufactured by STMicroelectronics, are reported. Bipolar transistors were irradiated by neutrons, ions, or by both of them. Fast neutrons, as well as other types of particles, produce defects, mainly by displacing silicon atoms from their lattice positions to interstitial locations, i.e. generating vacancy-interstitial pairs, the so-called Frenkel pairs. Defects introduce trapping energy states which degrade the common emitter current gain β. The gain degradation has been investigated for collector current Ic between 1 μA and 1 mA. It was found a linear dependence of ∆(1/ β) = 1/β i - 1/β (where β i and β are the gain after and before the irradiation) as a function of the concentration of Frenkel pairs. The bipolar transistors made on this technology have shown to be particularly radiation resistant. Both base and collector currents have been also systematically investigated.
Key words: Bipolar Transistor, Nuclear Irradiation, Frenkel Pair, Space Qualification
8th ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications
(Villa Erba, Como 6-10 October 2003)
D.CODEGONI1, N. CROITORU1,2, P. D'ANGELO1, G. FALLICA3, A. FAVALLI1, S. LEONARDI3, R. MODICA3, P.G. RANCOITA1 AND A. SEIDMAN1,2
Bipolar transistors were irradiated by neutrons, ions, or by both of them. Fast neutrons, as well as other types of particles, produce defects, mainly by displacing silicon atoms from their lattice positions to interstitial locations, i.e. generating vacancy-interstitial pairs, the o-called Frenkel pairs. The experimental results indicate that the gain variation is linearly related to the non-ionizing energy loss (NIEL) deposition for both neutrons and incoming ions.
1 INFN - Istituto Nazionale di Fisica Nucleare, sezione di Milano, Milan, Italy
2 Department of Physical Electronics, Tel-Aviv University, Ramat Aviv, Israel
3 STMicroelectronics, Catania, Italy
(Nucl. Instr. and Meth. in Phys. Res. B179 (2001). 397)
A. Colder1, N. Croitoru2,3, P. D’Angelo2, M. De Marchi2,4, G. Fallica4, S. Leonardi4, M. Levalois1, S. Marcolongo2, P. Marie1, R. Modica4, P.G. Rancoita2 and A. Seidman*2,3.
1 Lermat, Caen, France
2 INFN – Istituto Nazionale di Fisica Nucleare, sezione di Milano, Milan, Italy.
3 Department of Physical Electronics, Tel-Aviv University, Ramat Aviv, Israel
4 STMicroelectronics, Catania, Italy
In this paper it was shown that the irradiation with neutrons and carbon ions lead to gain degradation in bipolar transistors due to generation of defects. The density of these generated defects is independent on type of irradiation (neutrons or carbon ions). Thus, it is possible to evaluate D(1/b) , once the expected Frenkel pairs density is known.The dependence of the damage constant on collector current, is a power law function, with the exception of the lateral pnp transistors, that shows a higher sensitivity to radiation and a different behaviour. Neutrons give a smaller density of Frenkel pairs (CF) than the two sorts of carbon ions of high energy(CHE) and medium energy (CME). It was found that CME cause a higher concentration of CF. The calculated ratio R = CF/F , where CF is the Frenkel pair density and F fluence does not depend on F , for a given type of radiation. However, it depends on incoming particle type. Its smallest calculated value was obtained for neutrons (R= 6.1x10), which increases to 1.25x10³ for CHE and to 1.1x104 for CME.
Keywords: Bipolar transistors, Nuclear irradiation, Deterioration, Frenkel pairs.