The Relationship Between The Surface Defect State And Minority Carrier Lifetime Of Semiconductor

The surface defect state of semiconductor has a very important effect on the performance of semiconductor devices,especially crystalline silicon solar cells.The defect state on the surface can greatly change the photoelectric conversion performance.This paper mainly studies the correlation between the crystal surface morphology and the density of the defect state,the corresponding optical carrier life and the corresponding absorption spectrum theoretically and experimentally,in order to have a relatively systematic physical representation,so as to lay a certain theoretical foundation for the related technology research.Based on the basic theory of quantum mechanics,this paper deduce the preliminary relationship between the crystal surface barrier state density and surface defects by matrix method and the second chebyshev polynomial.The effects of different parameters on the density of the local states on the crystal surface are analyzed by computer simulation.Theoretical analysis shows that different surface morphologies correspond to different surface defect densities,and also have different effects on the optical carrier(minority carrier)life.Generally,if the surface microstructure has a sharp morphology,the corresponding surface barrier is relatively low,the surface defect state density is relatively high,and the lifetime of the minority carrier is relatively short.On the contrary,if the surface of the microstructure is in a non-sharp state,the potential barrier is relatively high,the corresponding surface defect state density is relatively low and the minority carrier lifetime is relatively long.In this paper,crystalline silicon surfaces with different surface microstructure were prepared by optimizing lye formula,and the surface morphology of different samples was given by scanning electron microscopy(SEM).SEM diagram shows that the surface with non-pyramidal morphology can be prepared on the surface of silicon as well as the surface microstructure with pyramidal morphology.The minority carrier lifetime of samples with different microstructures was measured by instrument.The results show that the sample with pyramids surface microstructure has a shorter minority carrier lifetime,which is due to the sharp tops and edges,resulting in a higher density of surface defect states,thus forming a large number of composite centers and reducing the lifetime of minority carrier.On the other hand,the non-pyramidal microstructures with uniform distribution have longer minority carrier lifetime.This is because the surface defect state of this microstructure is small.The infrared absorption spectra of various samples were measured simultaneously in this paper.It is found that the absorption on the surface of samples with different microstructures are different at the wavenumber of 8500cm^-1.The surface with sharp pyramids has higher absorption rate and the non-pyramidal surface's absorption rate is lower.This paper from the preliminary analysis:the surface covered with pyramids is easy to produce structural defects in the spire,edge and bottom,such as vacancies,impurities and other ions.These places are easy to produce the vibration absorption between atoms and ions,so the absorption is relatively high;These places are easy to produce the vibration absorption between atoms and ions,so the absorption is relatively high;And the non-pyramidal surface is relatively smooth in spire,edge and bottom,which cause the less structural defects,the vibratory absorption between its atoms and ions is smaller.The experimental results are in good agreement with the theoretical analysis.