The photoelectronic processes in p⁺ -n-p⁺ structures are studied for this investigation. The regularities of the width change of the adjacent barriers subject to the external voltage and the concentration of impurities in the base are revealed. The relations between these changes and the selective photo-sensitivity of the structure are shown. The possibilities of the effective registration of individual wavelengths from the integral radiation flux and the possibilities of the determination of the intensity and the length of these waves are analyzed. The necessity to develop a structure which will be used for the creation of a cheap, fast-acting system of optical analysis fit for use in the field is shown. The capabilities of the spectral selective sensitivity of the investigated photodetector structures are studied via obtaining the spectra of three LEDs (blue, green and red). The problems encountered are revealed and the solutions are suggested. The comparative analysis of the selective sensitivity and of the complexity of the production technology of the investigated photodetectors and that of the existing multilayer semiconductor photodetectors with active cascade-like layers is carried out. The possibility to carry out the optical spectral analysis by the investigated structures without the use of high-accuracy mechanical devices, light filters, prisms and diffraction gratings, and the possibility to apply the investigated photodetectors for the creation of multi-purpose spectrophotometers and monitoring systems which will be used for obtaining the information on the investigated medium and for solving the important security problems via conducting identification processes are studied.