Preparation And Photoelectric Properties Of Mg₂Si/Si Heterojunctio

As a non-toxic and non-polluting semiconductor material,Mg₂Si materials with their excellent physical properties have great potential for the preparation of photovoltaic devices such as solar cells and infrared detectors.Preparation of semiconductor material Mg₂Si heterojunction and its optoelectronic properties characteristics were studied in this paper.Mg₂Si films were prepared by co-sputtering and the effect of different power combinations on the preparing Mg₂Si films was investigated.Different structures of p-Mg₂Si/n-Si and n-Mg₂Si/p-Si photodiodes were then investigated,which provides a basis for the practical use of Mg₂Si-based photodiodes.Mg₂Si films are prepared by co-sputtering on silicon substrates and quartz glass substrates using a magnetron sputtering coating system.The effect of co-sputtering with different power combinations on the preparation of Mg₂Si films was investigated.The best power combination for co-sputtering was determined by characterization of the prepared films with XRD,SEM and Raman spectrometer:100 W for Mg target and 110W for Si target.The Mg₂Si films produced under this power combination had the best crystalline quality and the highest crystallinity,which laid the foundation for subsequent experiments.The p-Mg₂Si/n-Si heterojunction photodiodes were prepared,and their photovoltaic properties were investigated.The effects of p-Mg₂Si film thickness and n-Si substrate resistivity on the optoelectronic properties of p-Mg₂Si/n-Si photodiodes were investigated separately.The results show that the intensity of Mg₂Si（111）diffraction peak is gradually higher than that of Mg₂Si（220）diffraction peak with the increase of the film thickness.The SEM diagram shows that the best crystalline quality is achieved at a film thickness of 1600 nm.The results of its optoelectronic properties test show that the prepared Mg₂Si film is a p-type semiconductor,which is consistent with the doping type of the Si target.The intensity of the Raman peak is strongest at1600 nm,indicating the best crystalline quality of the film.The prepared p-Mg₂Si/n-Si photodiodes exhibit good spectral response characteristics between 800-1300 nm,and their EQE is consistent with the trend of spectral response change.At the p-Mg₂Si film thickness of 1600 nm,the peak response wavelength is 1190 nm,at which time the highest responsivity is 11.43 m A/W and EQE is 1.17%.Its V_oc,J_sc,FF,ηare 0.183 V,2.82 m A/cm²,30%,and 0.20%,respectively.The dark current decreases with increasing film thickness,and the maximum detection rate is 1.24×10¹² Jones.Subsequently,in experiments exploring different n-Si substrate resistivities（doping concentrations）,the spectral response improves as the substrate n-type Si resistivity decreases（doping concentration increases）,its peak responsivity increases to 12.83m A/W and the EQE increases to 1.32%.The photovoltaic performance is improved,but the dark current increases with the substrate doping concentration,and the detection increases first and then decreases,with a maximum detection rate of 1.30×10¹² Jones at substrate resistivities of 0.1 to 1 ohm/cm.The n-Mg₂Si/p-Si photodiodes were prepared by depositing different thicknesses of n-Mg₂Si films on p-Si substrates,and the effect of substrate resistivity（doping concentration）on photodiodes was investigated by selecting substrates with different p-Si substrate resistivities（doping concentration）.The results of the physical phase analysis show that the n-Mg₂Si film and the p-Mg₂Si film have the same trend with thickness.However,its overall photoelectric performance is better than that of p-Mg₂Si/n-Si photodiodes.These results provide experimental basis for the application of Mg₂Si in optoelectronic devices.