On The Changes In Optical Properties Induced By Heavy Ion Irradiation On AlGaN Films

A1GaN is one of the most important wide band gap semiconductor materials. Due to its’ outstanding properties, high frequency, high voltage and high power devices based on A1GaN can be widely used in domains such as space technology, nuclear power, and communication technology. Considering the irradiation environment in which the devices work, and the important role that ion-implantation and ion-irradiation play in device fabrication, the research of irradiation effect on A1GaN is important. For optical devices and optoelectronic devices, the research on the response of optical properties to the irradiation is crucial. The work in this thesis utilizes4MeV Kr ion to irradiate A1GaN/AIN film and then analyses the change of properties with respect to the ion implantation fluence.The UV-Vis-NIR transmittances are analysed and the refractive index, extinction coefficient, absorption coefficient are calculated by the envelope method and PUMA. Mechanisms responsible for the change in the refractive index and optical energy gap were discussed. The deep energy levels of defects induced by irradiation were analysed by the Lucovsky model. The optical band gap (Eg) were determined by the Tauc plot. The information of A1fraction and defect of AlGaN/AIN film were obtained by analysing the Raman spectrum. At high fluence, in the Raman spectrum there appear modes assigned to local vibrations of vacancy-related and interstitial-related defects. And there also appear mode attributed to disorder-activated Raman scattering. The red shift of the A1(LO) mode can also be attributed to disorder-activated Raman scattering. The photoluminescence spectrums reveal the appearance of the deep level defects related to impurities, vacancies, displacements raised by ion implantation. And the decrease of the intensity of the yellow luminescence can be attributed to non-radiative recombination related to above deep level defects.The general tendency of the change in the lattice structure and optical properties of AlGaN/AIN film respect to the ion implantation fluence are obtained by the work of this thesis. The results and the methods utilized in this thesis are useful for the research of the stability of the optic-electrics devices work under MeV ion irradiation. The tendency of the changes in optical constants of AlGaN/AIN film respect to the ion implantation fluence need to be explicated through further study.