Study On Al Doped Semiconductor Mg₂Si

In this paper,Al doped Mg₂ Si thin films were fabricated on Si substrates and quartz substrates by magnetron sputtering respectively,and the influences of different Al doping levels,Mg+Al film sputtering time and annealing temperatures on the crystal structure,surface morphology,electrical properties,reflection spectra,transmission spectra and optical band gap of Al doped Mg₂ Si thin films were investigated.First of all,the doping elements and doping methods were selected.After the discussion,it was determined Al-doped Mg₂ Si films were prepared by co-depositing Al and Mg on the Si substrate,and the Al-doped Mg₂ Si thin films on Si substrates were fabricated.The doping quantity is controlled by controlling the number of slices of Al chip.The Al-doped Mg₂ Si thin films with different doping amount of Al?0%,1.02%,1.58%,2.56%,5.81%?,Mg+Al film sputtering time?22.5 min,25 min,27.5 min?and annealing temperature?400?,450??were analyzed by X-ray diffraction?XRD?,scanning electron microscope?SEM?,atomic force microscope?AFM?,spectrophotometer,four probe,holzer tester.The crystal structure,surface roughness,optical absorption,optical band gap and resistivity of the samples were calculated and analyzed.The Al-doped Mg₂ Si thin films,the indirect value of band gap is between 0.423 and 0.495 eV?wavelength is between 2505 and 2931 nm?.The indirect values of band gap of undoped Mg₂ Si thin film is 0.53 eV?wavelength is 2175 nm?.The direct value of band gap is between 0.72 and 0.748 eV?wavelength is between 1658 and 1722 nm?.The direct values of band gap of undoped Mg₂ Si thin film is 0.833eV?wavelength is 1490 nm?.This means that the infrared detection wavelength is extended from the near infrared?wavelength less than 2500 nm?to the mid infrared wavelength range,which has important reference significance for the development of Mg₂ Si infrared detectors and other optoelectronic devices.The resistivity of the sample also decreased with the increase of Al doping amount,which indicates that Al doped Mg₂ Si thin films has better electrical conductivity,which is significant to the development of semiconductor devices using Mg₂ Si thin films.Finally,Al-doped Mg₂ Si thin films were prepared on quartz substrates.the test equipment and method of The Al-doped Mg₂ Si thin films with different doping amount of Al?0%,1.02%,1.58%,2.56%,5.81%?,Mg+Al film sputtering time?22.5 min,25 min,27.5 min?and annealing temperature?400?,450??are same of the sample on the Si substrate.It is found that the crystallinity of the samples prepared on the quartz substrate is not as good as that on the Si substrate.The reflection spectra and transmission spectra of the samples are not the same.The values of optical band gap of different Al doping levels were calculated.The direct value of optical band gap is between 1.15 and 1.40 eV.The indirect value of band gap is between 0.90 and 0.96 eV.The results show that the crystallinity of the films grown at 450? annealing temperature is better than that of the samples annealed at 400?.On the quartz substrate,the crystallinity of the films with Mg+Al sputtering time 20 min is better than that of the samples with Mg+Al sputtering time 16 min and 18 min.