The Fabrication Of Black Silicon And Its Application In Optoelectronic Devices Based On Femtosecond Laser Non-equilibrium Doping Technique

With the development of electronic industry, single silicon has been widely usedin microelectronic and optoelectronic devices. Comparing with other materials, singlesilicon has the advantages of low cost, easily refined, easily doped, easily integratedwith other optoelectronic devices. However, silicon has a wide band-gap, thereflectance of single silicon for240nm-2400nm is35%～40%, silicon based detectorscan not effectively detect the light longer than1100nm. Although Ge or InGaAs canmake up for the shortcomings of silicon, they cost lost and can not be integrated withexisting microelectronic and optoelectronic devices. In this thesis, we talk about a newform of silicon—black silicon, which has the advantages of low cost and easilyintegrated with devices, what’s more is that black silicon has near unity absorptance inthe wavelength region240nm-2400nm.The content of our thesis is to successfully fabricate black silicon samples withfemtosecond laser, and measure the surface morphology, optical property and electricalproperty of black silicon. Moreover, we polish waxsealed black silicon with traditionalgrinding method, the microstructures were cut by this method. The polished surfacecan be used for exploring the nature of black silicon.We successfully set up an optical system for the fabrication of black silicon, nowwe can easily make black silicon with special height and morphology. In addition, wecompare the influence of power density and pulses number on the morphology of blacksilicon.We fabricate a lot of black silicon under different conditions and measure therelation of reflectance, transmittance and absorptance with wavelength andexperiment parameter. Then we compare the influence of power density, pulsesnumber, scanning distance, different substrate and annealing temperature on theoptical property of black silicon.Based on the good optical property of black silicon, we make simple devices with area5×5mm~2,380×380μm~2, and140×140μm~2.We then test the rectificationcharacteristic and photo-response characteristic of devices. We find that the darkcurrent of devices is very high, the more is the reverse bias, the higher is the darkcurrent. All the devices have photo-response for808nm light. The responsivityincreases when the area of device decreases, the highest responsivity is300A/W forthe device with area140×140μm~2.To explore the doping characteristics of black silicon and make a clearunderstand of the transfer of carrier in black silicon, we successfully cut waxsealedblack silicon with traditional grinding method, then we make junction staining onpolished black silicon. Although we do not get the desired result, polishing blacksilicon is a good idea for us to enlarge the possibility of understanding black silicon.