Nanocrystalline Silicon Electroluminescent Enhance Research

Modern photoelectronics based on silicon calls for integration of light source, waveguide, WDM, grating, detector and other related functional devices onto one silicon chip. Developing light source from silicon is the last obstacle in achieving this goal. Silicon nanocrystals embedded in SiO2(nc-Si:SiO2) is considered a promising silicon light source material. For electroluminescence from silicon nanocrystal, the carriers injection and combination to light emission is the most challenging work.This dissertation starts with a brief introduction to the developments of light emission from silicon nanocrystals. The luminescent principles of porous silicon and nc-Si:SiO2and relative merits are elucidated. Then several methods to fabricate silicon nanocrystals are reviewedsuch as CVD, PLD, Ⅱ and PVD in detail. Several tests including PL, Raman and TEM are employed to characterize the physical and chemical properties of nc-Si. The relationships between excitation and PL intensity are studied by pumping the film containing nc-Si with various wavelengths of light. It is found that light with300nm in wavelength iseffective to gain strong PL. The samples are passivated in H2:N2mixed gas to achieve higher PL increasement. The best passivation environment is400℃and half an hour.After discussion of preparing samples, one chapter features EL from nc-Si. In this chapter, we show how the samples are made and the relationships between voltage and current studied. It is found that when the voltage keepsincrease, the current firstly increases and drops after reaching its peak. If the voltage continues to increase, the current turns up again.In the next part of this work, we studied the EL and PL enhancement through fabrication of multilayer samples of Si/SiO. Nc-Si’s are formed in both SiO and Si layers after annealing in furnace. The Si interlayers help to increase the PL intensity and there is a certain thickness for Si interlayers to obtain strongest PL. Also, the Si interlayers introduce extra carrier transportation paths to archive EL emission. A comparative study is further performed on a multilayered Si/SiO sample and a single-layered one with Si and SiO homogeneously mixed. Both samples have the same ratio and contents of Si to O. The multilayered samples overwhelm singlelayered samples in higher EL intensity, lower turn-on voltage, lower resistance, and higher current efficiency. These results indicate that Si interlayers in Si/SiO may act as carrier channels, which promotes carrier transport and enhances the EL emission of Si-nc.Furthermore, we study the laser pre-annealing on the electroluminescence of nc:Si.It is found that after such a laser pre-annealing treatment, both the PL and EL of nc:Si are considerably enhanced. The EL intensity of nc:Si evolves in a similar up-and-down manner as the PL one with the increasing laser power and dot density. The intensity of PL and EL is a compromise of the density of nc:Si and defect.In the last part of this dissertation, ITO top electrode is adopted and the cooling system is applied when measuring EL. Some interesting phenomena are observed and discussed.