Dislocations, extended defects and interfaces at nanoparticles as effective sources of room temperature photo- and electro-luminescence in silicon and silicon-germanium

none8In view of demonstrating the technical feasibility of silicon based, high efficiency room temperature light emitting devices (LED), the primary objectives of this Project are: 1. to find practical approaches for the creation of suitable dislocation structures or of alternative structures (like misfit dislocations in Si-Ge heterostructures, dislocation loops at Si/SiO2 interfaces and Si nanocrystals in amorphous silicon) such to enhance the quantum efficiency of the dislocation-related luminescence (DRL) or of the intrinsic emission of silicon at room temperature in view of applications for silicon-based LEDs. To this purpose, several processes of dislocation generation will be employed, in addition to the conventional plastic deformation at high temperature 2. to obtain a clear understanding of the physics of the dislocation-assisted light emission, of the correlations between the dislocation structure and their emission properties, of the role of carbon, oxygen and other light impurities like hydrogen and nitrogen as well as of metallic impurities on their emission properties and of the correlation between device surface quality, configuration and luminescence yield 3. to carry out theoretical investigations on the correlation between core structure of extended defects and optical and electronic properties of dislocations About the first topic, the photo-(PL) and electro-luminescence (EL) emission of dislocations generated by different means will be studied in clean conditions. Different dislocation structures will be generated by special deformation procedures, by ion implantation or by the injection of self-interstitials or vacancies generated in a silicon matrix during the growth process of a precipitate having a different molar volume of the matrix, as it happens with SiO2, SiC and Er-oxide in heat treated carbon loan and carbon doped Cz silicon, carbon- implanted FZ silicon and Er-implanted Cz silicon. Also Si-Ge heterostructures, interesting because potentially compatible with conventional microelectronic processes will be studied, before and after strain relaxation. The second topic will be treated by studying the effect of all the mentioned impurities on clean dislocations prepared by plastic deformation of Fz or Cz silicon, whose cleanliness will be tested by photoluminescence (PL), Deep Level Transient Spectroscopy (DLTS) and lifetime mapping measurements. The effect of impurities on the light emission features of oxygen precipitates will be also studied. Eventually, the correlation between dislocation structure and optical properties will be studied using different computational methods, as the scc-DFTB (self consistent charge functional based tight binding method) and the AIMPRO (ab initio modeling program) http://intas.mater.unimib.it/noneB. Pichaud; A. Cavallini; S.Pizzini; N.Sobolev; E.Yakimov; V.Kveder; R.Steinmann; R.JonesB. Pichaud; A. Cavallini; S.Pizzini; N.Sobolev; E.Yakimov; V.Kveder; R.Steinmann; R.Jone