The growth and characteristics of the detector p-i-n-structures fabricated by means of the epitaxial methods are discussed. High-resistivity i-layers containing chromium as a compensated impurity have been grown on the n-GaAs substrates by the liquid-phase epitaxy method. The layer thicknesses are (150-250)μm, their resistivities lie in the interval ρ=(5x10 6 -2.5x10 8 )ohmcm. The thin Zn-doped p-layer has been grown upon the i-layer by the vapour-phase epitaxy method. The electric field profiles in the p-i-n-diodes have been measured. The reverse current-voltage characteristics of the diodes have been analysed. The sensitivity of the structures to β- and γ- radiations has been investigated.