Gontaruk O. Degradation and relaxation processes in GaP light diodes stimulated by ultrasonic and radiation

The dissertation concerns the study of GaP p-n- structures. Degradation- relaxation processes in GaP samples, treated by ultrasonic and gamma irradiation are studied. The ultrasound influence on the defects of technological and radiation origin of GaP light diodes has been investigated. GaP light diodes were treated by ultrasound wave (oscillation power 1 W/cm-2, frequencies - 3-9 MHz) in different operating modes. Electroluminescence spectra were measured at room and low (77 K) temperatures, integrated luminosity of devices was checked by solar cell. In crystals, treated by ultrasound at 77 K low-frequency oscillations of the luminescence intensity appear, which are synchronous with those of the current. The oscillations mentioned, are caused by the formation of mobile dislocations domains involved in the creation defects of dark lines and defects of dark spots. In order to find out the radiation field influence on non-equilibrium defects of acoustic origin samples were irradiated at room temperature by gamma rays of Co60 (D = 102 Gr). It has been discovered that in GaP light diodes treated by ultrasound unstable at room temperature dislocation networks occur at the volume of crystal. Ultrasound dose increase causes the creation of complex defects with high relaxation time and appearing of a part of more mobile defects, which relax quicker. The nature of effects discovered has been discussed. The method of the emissive capacity restoring of samples degraded after irradiation have been proposed. From the analysis of the degradation-relaxation modifications under irradiation it's dear that the main reason of their appearing is the movement of dislocations and the creation of dislocations network, stimulated by the high ionization level. Degradation-relaxation process back-displace GaP light diodes have been studied after ultrasound treatment and electron-irradiation. The main feature of effect US on a microplasma luminescence is in a small of restoring of brightness during a relaxation. The positive operati on of ultrasound is a corollary of interaction of driving dislocations with non-equilibrium congestion's of defects. The exposure by electrons by small dozes (Е=1 MeV, Ф > 1015 cm-2) diodes GaP reduces intensity of a microplasma luminescence (10 - 20 %), the magnification of a doze of an exposure results in increase of volume i- of a stratum. Such increase happens owing to origin of deep levels in p-n- transition. Ultrasonic wave is shown to be the promising tool for improving characteristics of GaP light diodes with high concentration of defects.