讲座题目：Investigation of an interaction of hadrons with Si and GaN during the irradiation and properties change afterwards.

辐照条件下强子与Si和GaN的相互作用及辐照后的特性变化

讲座人：Juozas Vidmantis Vaitkus立陶宛科学院院士

时 间：10月22日下午3:00-5:30

地点：北二楼1415会议室

讲座内容：

Silicon has been widely used in the fabrication of microelectronic devices. In addition, GaN has shown high resistance to radiation, and is promising for applications in harsh environment. As Si and GaN are used or proposedasmaterials of radiation detectors and optoelectronic devices applied in ionizing radiation environment (high energy physics, space research), an investigation of radiation-induced defects in the two materials is important.

It has been demonstrated that the cluster formation is mainly contributed by the kick-off silicon atoms. The disordered regions created by atomic displacements leads to modifications in the electron band structure around and inside the cluster.With the density functional theory (DFT) methods, the electronic states in the cluster were calculated. The free carriers generation and recombination was investigated for samples irradiated by neutron and proton beams, as well as reactor neutrons. The possible structure of cluster was proposed by analyzing the influence of the irradiation on the electrical and photoelectrical properties of silicon. The dependence of free carrier lifetime on clusters in a wide range of fluence was observed, which is promising for the proton beam imaging and the monitoring of hadron irradiation. Due to the difference in atomic packing, GaN is more radiation-resistant than Si, which indicates the dependence of radiation hardness on crystal structures. GaN samples, grown by MOCVD method on sapphire substrates, were irradiated by ionizing irradiation. Disordered regions were observed and the volume of those regions increased with radiation dose. These regions around the submicron structural defects lead to a wide-range variation in capture time for free carriers. The influence of defect clusters and their influence on electronic properties are crucial to predict the properties of devices irradiated by hadrons. The Synopsys TCAD simulator was used to model the macroscopic effects of cluster defects introduced into semiconductor devices.

讲座人介绍：Juozas Vidmantis Vaitkus，立陶宛科学院院士

Juozas Vidmantis Vaitkusis Professorat Vilniusuniversity and director of Institute of AppliedResearch. His Awards and Elections are as follows:National Awards for Scientific Achieve in Physics, USSRStateAward for Novel Engineering, Award for Scientific Achieve in Microelectronics of Lithuanian Council of Ministers, Chairman of Physics Section ofLithuanianAcademyof Science, deputy-chairman of CERN RD50 collaboration board, President of Lithuanian Physical Society and member of European Physical Society board

His research interests are inSi, GaN, GaAs, TlBr, SiC, crystals and structures as well as the tissue cells.He has authored above 350 in reviewed journals and editions (Physics and Engineering, Biomedicine). He has 17 technical author certificates and patents in electronics, optoelectronics and measurement technology.