Preparation And Photoluminescence Study Of Silicon Cavity Films

As the second most abundant element in the earth’s crust,silicon began to be used in electronic devices in the 1950s.With the development of technology and the improvement of integration,it began to be widely used in the field of integrated circuits and chips.In recent years,the research on silicon-based optoelectronic devices has become a hot spot.At present,a series of passive devices have been fabricated on silicon.However,due to the indirect band gap structure of silicon(the band gap width is 1.12 e V),it has extremely low luminous efficiency.How to develop a better light source on silicon has become a difficulty.In this paper,the low-dimensional structure of silicon,nano-silicon structure,was prepared to study its luminescence mechanism.In this paper,non-polluting pulsed laser etching(PLE)and pulsed laser deposition(PLD)were used to prepare silicon-based cavities and thin film structures with better photoluminescence intensity by changing different parameters.The main research contents are as follows:(1)A large-scale(100)oriented silicon quantum surface structure was established by using Materials Studio software.Corresponding to the film structure of silicon during the experiment,four quantum surface structures were established near 8nm-30nm,and the self-consistent band gap total energy of quantum surfaces at different scales was calculated respectively.The calculation results show that the quantum confinement(QC)effect is still consistent in the larger-scale silicon quantum surface.A small-scale(100)oriented silicon quantum surface structure is established.When the thickness is close to the single atomic layer,the anomalous QC effect appears,that is,the band gap plummets,and a structure similar to the Dirac cone appears.The band gap disappears,which is attributed to the change in the dimension of the symmetry breaking of the quasi-two-dimensional structure.(2)The influence of parameters such as pulse laser etching time and annealing time on the luminescence of silicon-based cavity array structure is studied.By changing different preparation and post-processing parameters,we explored the conditions under which the samples prepared have better photoluminescence intensity.The experiment used a nanosecond pulse laser with a wavelength of 1064 nm,a power of 30 W,an average pulse width of 100 ns,and a frequency of 1.6 k Hz.The etching time of a single cavity is 5s,6s,7s,and 8s,respectively.The silicon-based microcavity array was prepared and its photoluminescence(PL)was tested.The experimental results show that the number of photons of the cavity sample obtained at 6s is the highest,instead,the photoluminescence intensity is the highest;(3)The samples prepared by etching 6s were annealed at 1000℃ for 10,20,30 minutes to observe the change of PL intensity of the samples,and the luminous intensity before and after annealing was compared.The results show that the quantum dots are generated and embedded in the cavity during the etching process of the laser on the surface during the preparation of the samples.Therefore,a higher number of photons can be shown in the PL spectrum with a lower power excitation light,and the emission wavelength is about 700 nm.It can be explained that the density of small quantum dots is more concentrated at this time.After annealing,quantum dots grow and the photoluminescence intensity reaches the best when annealed for 20 minutes.The experimental results are analyzed.(4)The experimental results show that after coating on the surface of the cavity,the luminescence at the edge of the cavity will be enhanced,which is attributed to the fact that the density of quantum dots at the edge of the cavity has been improved again after coating.However,on the surface of the silicon wafer outside the cavity,the photoluminescence intensity is slightly enhanced after coating,but the intensity is not much improved.(5)The PLE method was used to etch a microcavity array containing nano-silicon with a diameter of about 25μm on a silicon wafer.The thermal annealing treatment was carried out at1000℃ for different times in an oxygen-filled environment.The PL spectrum of the test sample was changed by changing the excitation light power,and the PL spectrum at each power was fitted and analyzed.The power curve at each annealing time was analyzed.It was found that the sample had a strong photoluminescence in the cavity before annealing.The peak of luminescence is about 700 nm,and the peak of photoluminescence spectrum after annealing for 10 min is around 750-800 nm.The QC effect can be used to analyze the size growth of silicon quantum dots in the sample.Significant spontaneous luminescence characteristics can be observed by analyzing the power curve of the sub-peak at 850 nm after annealing for 10 min.However,after annealing for 20 min,the sub-peak power curve near600 nm shows a superlinear trend,and the excitation threshold is 6.7×10~4W/cm~2,indicating that the characteristic luminescence of oxygen-doped Si-O-Si bridge bond appears after annealing for 20 min.The model of electron transition is established to explain the mechanism of the excited light.(6)The external quantum efficiency of the sample without annealing was studied,and the relationship between the annealing time and the external quantum efficiency was studied.The external quantum efficiency of about 18%was obtained in the silicon microcavity.