Mamontova I. Photoelectrical and optical phenomena in photodetectors and solar cells on the base of A3B5 semiconductors with textured interfaces.

The dissertation is devoted to the research of the photoelectrical and optical phenomena in the photodetectors and solar cells on the base of A3B5 semiconductors with textured active interfaces. Influence of microrelief interface between thin conductive film (emitter) and semiconductor substrate (absorber) on the optical and recombination losses in surface barrier solar cells is analyzed. Equations for the calculation of monochromatic light transmission through a thin absorbing film with one or two rough surfaces, on an absorbing substrate, are presented. The possibility to increase the photosensitivity of the Au/GaAs surface barrier structures (SBS) due to texturization and sulfur passivation of the interface for two types of microrelief (dendritic or quasigrating) obtained by chemical anisotropic etching has been investigated. The recombination parameters of textured interfaces were determined from the experimental spectra of the external quantum efficiency, taking into consideration the calculated spectra of light transmittance. A comparison of the internal quantum efficiency spectra with calculated ones allows a determination of the electronic parameters of the interface. The application of fluctuation model with Gaussian type of lateral barrier height distribution to the simulation of photoelectric and dark electric I-V characteristics of metal/semiconductor SBS with rough interface has allowed explaining their certain special features by a difference in the width of this distribution . In addition to the increase of the effective value of Richardson constant and the apparent temperature coefficient of the barrier height, the decrease of the open-circuit voltage of fotodetectors and solar cells with the increase is predicted. The comparative investigation of Au/GaAs SBS with interface microrelief of dendrite- and quasigrating type verified the theoretical prediction. Specifically, the smaller Voc value in the case of SBS with dendrite-type microrelief at nearly equal Isc was explained by a greater that was confirmed by a greater width of microrelief height distribution obtained from atomic force microscopy (AFM) data. Photodetectors with enhanced UV response which is comparable to and even exceeds that of known devices in the spectral range from 0.25 to 0.4 m have been elaborated on the basis of Au/(GaAs, InP) structures by means of developed technology of chemical processing including texturation of the heterojunction interface. Both the photoconversion parameters under AM0 simulated illumination and the tolerance for 60Co -irradiation, obtained for structures with various interface microrelief morphologies, allowed identification of the quasigrating type as more suitable for solar cell application.