First-principles Study Of Infrared Absorption Mechanism Of Black Silicon Based On Doping Of Inert Elements

As a widely used semiconductor material,silicon has been widely used in photodiodes,photodetectors,photovoltaic devices and many other fields.However,the high surface reflectivity and large band gap of conventional bulk silicon limit the full utilization of the spectrum.To solve this problem,many methods have been developed.Among them,silicon with surface nanostructures,namely black silicon,has the highest efficiency and is the most widely used.Due to its high absorption in a broad range from UV-visible to infrared,black silicon has promising applications in photodiodes,photodetectors,solar cells,field emission,luminescence,and other optoelectronic devices.The current research shows that black silicon has low reflection and high absorption properties and that the devices made of black silicon have a response extending into the infrared spectral range.Although the application potential of pulsed laser black silicon is huge,its development has been slow in the past 20 years,which is largely limited by the complex physicochemical structure in the pulsed laser black silicon layer.It was reported that a black silicon material doped with inert atoms(argon atoms)obtained by ultrafast laser processing can be fabricated into a photodetector with excellent performance in the communication optical band.Through first-principles calculations,a new dynamically stable superatomic structural defect was discovered.By analyzing its internal microstructure and dynamic properties,the process of the interaction of argon atoms as a substitution impurity with the silicon lattice was obtained.The electronic structure of the system was calculated,the influence of the defect on the silicon energy band structure was determined,and the physical mechanism of the introduction of inert atoms to enhance the infrared absorption of silicon material was theoretically proposed.The proposed mechanism provides a theoretical basis for the application of inert atom doping in silicon-based optoelectronics.It is believed that laser irradiation would also produces a variety of amorphous phases that contribute significantly to infrared absorption in black slicon.However,due to the complex light-matter interactions,the local structures,structure-property relationships and formation laws of these amorphous phases are not well understood.Through first-principles molecular dynamics simulation,a series of amorphous silicon atomic models was obtained by melt quenching method.Depending on the cooling rate,varying degrees of twisted or constrained local structures are formed,while sp3 hybridization is mainly retained in amorphous silicon.The faster cooling rate leads to a more disordered local structure,thereby introducing more defect states in the band tails or band gaps,which contributes to improved infrared absorption.Furthermore,around the glass transition temperature,the energy and structure of liquid silicon undergo dramatic changes to form an amorphous solid,indicating a key process that determines the amorphous structure.