Microstructure Silicon-based Near-infrared Materials And Its Optics,Photoelectric Characteristics Research

According to the sort of chip material,the imaging sensor could be divided into visible light image sensor on silicon based material and infrared imaging sensor on non-silicon based material.Compared with the non-silicon based imaging sensor(for example,InGa As/HgCd Te material based senor),silicon image sensor has more mature manufacturing process,low cost,simple structure,can work at room temperature,strong stability to resist the environment,and many other non-silicon image sensor incomparable advantages.Though the silicon image sensor has been widely applied in people's daily life(such as the core of the imaging element in mobile phone cameras and SLR cameras are made of silicon based CMOS image sensor).But its photosensitive area mainly focused on the visible spectrum(< 1.1 microns),which seriously limits the application of it in the infrared wavelengths.The scientists come from the university of harvard American success prepare a kind of new silicon based material with surface microstructures,which know as "black silicon" material.The spikes surface microstructure is formed by femtosecond laser processing.This kind of material have two characteristics,very low reflection and high absorption in both visible and near infrared region,due to the surface microstructure and high concentration doped level.Compared with the traditional silicon detector,the detector prepared by black silicon has the following two extremely attractive properties:(1)the higher degree of response;(2)the wider response in the visible to near infrared region.Combined with the properties of the silicon image sensor,it can overcome the non-silicon-based infrared imaging sensor manul technology and device structure complex(for example,mismatch with the silicon's lattice caused the non-silicon-based always need complex indium column connection between the chip and readout circuit,etc),high cost and poor ability to resist environmental drawbacks,the black silicon near infrared imaging sensor in military and civil fields will have wider application prospect.The new silicon microstructure near-infrared light electric materials prepared by femtosecond laser processing in a special atmosphere environment.Traditional silicon-based imaging sensors have weak response in near infrared wavelengths and cannot achieve the near infrared imaging.The new type of silicon near infrared optical properties of high absorption materials and photoelectric response characteristics are studied.Explore the new silicon-based materials in visible,near infrared wavelengths light absorption characteristics and action mechanism of photoelectric response,hope to get higher absorption in the visible to near infrared region and wider response wavelength of new silicon-based near-infrared photoelectricity materials.The paper main work is as follows:1.Get the new surface microstructure silicon-based material by femtosecond laser irradiating the silicon surface in SF6 atmosphere processin.Research the relationship between the black silicon surface microstructure morphology and femtosecond laser processing,the near-infrared light absorption enhancement effects impacted by the black silicon surface microstructure formed in femtosecond laser processing.Explore the the influence of S elements which doped by the femtosecond laser processing in SF6 atmosphere environment in black silicon on wide spectral absorption characteristic.By studying the femtosecond laser irradiation energy density,processing factors such as atmosphere environment for the formation of the microstructure morphology and the role of the S elements doped in silicon materials to explore the method of making the black silicon which has widly high visible-near infrared absorption.By further study on the basis of physical process of femtosecond laser manualed black silicon material,we get the black silicon with a consistent high absorption properties,from 400 nm to 2500 nm wide spectral reflectance on average is below 5%,the average absorption is higher than 90%.Based on a high doping concentration silicon substrate,we prepare a new kind of black silicon which has high temperature stability.2.The formation mechanism of silver nanoparticles on black silicon surface and its influence on infrared absorption are studied: we fabricate a large number of irregular and random distributed silver nanoparticles on the surface of black silicon microstructure by electron beam evaporation and shadow effect of thin film deposition;In near infrared band,these silver nanoparticles makes up for the insufficient absorption of the small-scale silicon surface microstructure prepared by low laser power density,which can make the absorption rate of small-scale silicon surface microstructure increase to 90% in wide near infrared band;Aiming at the problem of infrared absorption degradation of black silicon after high temperature annealing,plasmon resonance method excited by metal nanoparticles is proposed to compensate the infrared absorption degradation of black silicon material after high temperature annealing,making up for the infrared absorption efficiency of black silicon materials after high temperature annealing.3.The high photoelectric response mechanism of black silicon photoelectric materials in visible-near infrared band is studied: the influence of basal mixed type and concentration on element S supersaturated doping and photoelectron of black silicon photoelectric materials;The mechanism of lattice defects and polysilicon formation in femtosecond laser processing is studied,exploring the method that improving the photoelectric response by reducing defects;The repair function of high temperature heat treatment process for lattice defects and polysilicon formation caused by the femtosecond laser machining process,and the influence of photoelectron extracting in black silicon photoelectric material.On the basis of further study of high photoelectric response mechanism of black silicon photoelectric material in visible-near infrared band,a new silicon-based near infrared high response material is obtained.I ts light response expands to infrared wavelengths,and is dozens of times higher than normal commercial silicon detector----our black silicon photoelectric detector's average response is up to 14.3 A/W in 400-1100 nm band,the highest response is 24.5 A/W,and the average response is 71 ma/W in 1200-1500 nm infrared band.