Lifetime evolution of carriers in junction diodes irradiated by high-energy protons

The work described in this thesis is devoted to the analysis of the degradation phenomena under irradiation of the P-N junction diode which is the basic element of all minority carrier devices. This study is carried out in a perspective of prediction of the degradation of the electrical properties of the devices and research of a better behaviour to nuclear radiation. The methods and experimental devices used for lifetime measurement are presented in Chapter II. A method for automatic lifetime determination in diodes is developed taking into account the expressions established in the first chapter. The diffusion length in solar cells is obtained by photovoltaic effect and the lifetime in single crystals is deduced from photoconductivity pulses. Particular importance is given to the evaluation of the injected carrier rate. The experimental study of the lifetime degradation by high energy protons required an experimentation at the large particle accelerators: Saturn proton synchrotron and CERN synchrocyclotron. Chapter III provides the main characteristics of the proton beams used and presents all the values of the degradation constants obtained with high energy protons (3000 MeV, 600 MeV and 207 MeV), and with particles creating less complex defects (electrons of 4.5 MeV and protons of 10 MeV). Chapter V presents some applications of the results obtained. The observed lifetime variations are applied to the prediction of the degradation of the current-voltage characteristics of diodes. Moreover, concrete objectives are reached from the analysis of the lifetime evolution: improvement of the speed of switching diodes and finally 'hardening' of solar cells. (O.M.)