GaAs peculiarities related with inhomogeneities and the methods for reveal of their properties

The inhomogeneities in as-grown and irradiated GaAs crystals and structures, their properties and role have been analysed. The influence of inhomogeneities on the properties of crystal and Schottky diode structure are presented. The possibilities of different methods for material and structure characterisation (Hall effect and magnetoresistance, noise spectra, thermally stimulated current and polarisation, photoconductivity kinetics and spectrum, light-induced diffraction) are discussed. Existence of the inhomogeneity of the crystal structure has been revealed by diffusion of copper through the GaAs wafer, and a percolation of it through doped crystal has been determined by means of the Hall effect. Modification of the recombination-induced defect system has been analysed to get deeper insight into the crystal and device degradation under illumination by ionising radiation. Role of free carriers in local electric field generation has been analysed via modification of the EL2 centre in GaAs. Complicated behaviour of non-equilibrium conductivity during quenching and activation of EL2 centres has been determined by precise measurement of the photoconductivity spectra in different crystals. Influence of the EL2 centre on the non-linear polarisation of sample and on the additional non-active light absorption has been analysed