The Luminescence Property Of Silicon-based Light Emitting Materials Prepared By Ion-implantation

Nowadays,more and more transistors are integrated in chips as the integrated circuit advances according to the Moore's law.Chips become smaller,faster and cheaper.At the same time,the structure and length of the metal interconnection become overwhelming,which will worse problems such as cross talk,energy dissipation,etc.Moreover,the parasitic resistence and capacitance of the planar CMOS will exceed its channel resistence and capacitance with the scaling of feature size.On the other hand,the ever-growing global optical communication is severely hampered by the "bottleneck" of the data transmission of short-distance metal interconnection.Finally,the development of the integrated circuit includes not only the increased integration level of ultra-large-scale integrated circuits (ULSIs)but also the expanding of applications such as sensors,mechanics,fluid, and optics,etc.The chips need to have the function to process optical singles in optics system.All these challenges require the emergence of silicon optoelectronics system,among which the silicon-based light emitting device is the key opponent and therefore,the main objective of this thesis.Silicon-based light emitting materials and devices,including silicon pn junction,rare-earth Tb³⁺doped SiN_x and SnO₂ films,were fabricated by ion-implantation and their light emission properties were studied in this thesis and some significant results were achieved as follows:Firstly,silicon pn junctions were prepared by ion-implantation and subsequent annealing process and their low temperature and room-temperature photoluminescence(PL)properties wereinvestigated.The defect microstructures and carrier recombination at dislocation loops region were characterized by transmission electron microscope(TEM)and electron beam induced current (EBIC),respectively.Results show that the light emission of pn junction is independent of ion types(B or P).PL intensity firstly increases and then drops down with the increasing ion-implantation dose.PL intensity of pn junction prepared by furnace annealing is higher than that by rapid thermal annealing (RTA).And hydrogen annealing can further improve the light emission intensity. The annealing temperature should be controlled in the range of 950-1100℃.The light mission from bounded excitons at low temperature is enhanced.After ion-implantation and high temperature annealing,dislocation loops are formed in the pn junction.Carrier recombination at the dislocation loop region is intense at room-temperature.No dislocation-related luminescence is found.The quantum confinement effect at the edge of dislocation loops is the main mechanism of the light emission from silicon pn diode at room-temperature.Secondly,SiN_x films were deposited by plasma-enhanced chemical vapor deposition(PECVD)and Tb³⁺ions were introduced by ion-implantation.The effects of post annealing on luminescence properties of the SiN_x:Tb³⁺thin films were investigated.Furthermore,SiN_x films with different silicon concentrations were deposited by PECVD with varying reactive gas ratio of SiH₄ to NH₃.And the effects of these different SiN_x substrates on the light emission of Tb³⁺ions were measured.Results show that ⁵D₄→⁷F_k(k=6-3)series luminescence lines of Tb³⁺ions is observed in SiN_x:Tb³⁺films and the PL intensity increases with annealing temperature(≤1000℃).The SiN_x:Tb³⁺thin films have little temperature quenching of light emission.Little oxygen content,energy transfer from defect related states,carrier mediated and short light emission lifetime are the reasons for the improved light emission of Tb³⁺in SiN_x:Tb³⁺film.Light emission of Tb³⁺ions can be found in different SiN_x host materials.But in silicon rich SiN_x(SRSN)films,silicon nanocrystals precipitate from the matrix after annealing at high temperature.And the SRSN film is easy to be oxidized.The PL intensity of the Tb³⁺is decreased by the two factors. Thirdly,SnO₂ thin films were fabricated by high temperature oxidation and reactive magnetron sputtering(RMS).Microstructures and formation mechanisms of these films were characterized and analyzed,respectively.Room-temperature PL and electroluminescence(EL)of SnO₂ films were studied.Moreover,Tb³⁺ doped SnO₂ films(SnO₂:Tb³⁺)were prepared by ion-implantation and subsequent annealing process.And its room-temperature light emission properties were investigated.Results show that pure tetragonal rutile structure SnO₂ films are formed by oxidation of Sn films at 1000℃and intense oxygen vacancy related luminescence at 590 nm are detected at room-temperature.The luminescence intensity of this line decreases with the increasing of oxidation time.The light emission at about 590 nm is also observed in SnO₂ films prepared by RMS and high-temperature annealing.The SnO₂ film is proved to be a good candidate of silicon-based luminescent materials by the EL of SnO₂/p-Si heterojunction when forward-biased.The light emission from Tb³⁺ions from SnO₂:Tb³⁺film annealed at 1000℃is observed and coexists with the host SnO₂ defect luminescence.The light emission of Tb³⁺ions is enhanced and the light emission of the defect-related luminescence from SnO₂ is suppressed by the P diffusion into the SnO₂:Tb³⁺ films.