Research On The Photoconductive Properties Of Ho_1-xCa_xMnO₃ And Ca_1-xSr_xIrO₃

The narrow bandgap semiconductors have a bandgap width of less than 0.5 e V and has important application in infrared detectors and so on.At the same time,the bandgap structure of the narrow band gap also makes it attract people’s attention in terms of physical research and other aspects.The narrow bandgap semiconductor HoMnO₃ is a typical multiferroic material that has both ferroelectric and ferromagnetic properties.Researchers through in-depth analysis of the doping of Ho_1-xCa_xMnO₃ conductive mechanism found that at low doping concentration,it belongs to the one-dimensional range jump conduction mechanism.However,the one-dimensional conduction model in three-dimensional blocks has not been well explained so far.The photoconductivity effect of Ho_1-xCa_xMnO₃ was tested for the first time in this paper,and the photoconductivity effect of Ho_1-xCa_xMnO₃ with temperature was analyzed.In order to explain the incomprehensible conduction mechanism in Ho_1-xCa_xMnO₃,we introduce the external factor of illumination,which influences the conductivity of the sample,and from another point of view,the conduction mechanism of the sample.Compared with the temperature-variable resistance experimental data,we believe that there is only a thermally activated conduction mechanism in Ho_1-xCa_xMnO₃.The temperature-variable resistance experimental data cannot be linearly fitted using the heat-activated model formula because its band gap widens with increasing temperature.We then tested and fitted the photocurrent relaxation recombination phenomenon at different temperatures,and obtained the law that the relaxation time constant increases as the temperature increases.Based on the analysis of the law of relaxation time constant with temperature and doping ratio,we consider that Auger recombination in Ho_1-xCa_xMnO₃ is the main mechanism of photocarrier recombination.In addition,we conducted a comparative test on the post-perovskite compound Ca_1-xSr_xIrO₃ to determine the correctness of the proposed theory.Ca_1-xSr_xIrO₃ has a post-perovskite structure,and samples with low doping concentrations belong to narrow bandgap semiconductors.The results show that with the increase of Sr2+ doping ratio,the resistance of Ca_1-xSr_xIrO₃ decreases obviously,and further doping will make it eventually become metallic.We also conducted a test of the temperaturechanging photoconductive effect and the constant-temperature photocurrent relaxation composite effect,and reached a conclusion similar to Ho_1-xCa_xMnO₃,that is,it belongs to the themal-activated conduction mechanism,and its bandgap increases with temperature.Broadening,in the sample,Auger recombination played a major role.