Photoluminescence From Si₃N₄ Films Implanted With High Dose Si Ions

Recently, new semiconductor materials with effective luminescence properties are urgently needed for the rapid development of microelectronics industry. Silicon as a widely used material is of limited used for optoelectronics applications because of its poor light emission resulting from its indirect band gap structure. Although many methods have been explored to fabricate nano-crystal silicon, which could result in strong luminescence in a wide band, the most promoting one among them may be by ion implantation, owing to its compatibility with conventional Si device technology. Up to now, many researches have been made to study luminescence properties in ion implanted SiO2 film and the involved mechanisms, few studies have been paid for the similar effects in ion-implanted Si3N4 films. In this study, based on the results from Si implanted SiO2, we have study the photoluminescence properties in Si-implanted Si3N4 films in detail. The Si ions were implanted at room temperature at 80 keV and at a dose of 1×1017 ions/cm2. Our results clearly show that similar to that observed in SiO2 film, high dose Si ion implantation into the Si3N4 films induces a strong blue and violet light emission. The PL intensity has been found to decrease with annealing temperature. According to the results from electron spin resonance (ESR) measurements, we suggest that the blue and violet light emission band can not be only attributed to the implant-induced broken Si-bonds. It may be also related to other defects, such as, N vacancies and the dislocations and etc. Moreover, as for the annealing temperatures higher than 900℃, new luminescence bands at about 700 and 930 nm were also observed. The intensity and peak position of these bands were found to depend strongly on the annealing temperature. These PL bands can be attributed to the formation of nanometer Si crystals with different sizes in Si3N4. Theoretical calculations have indicated that corresponding sizes for the above two bands were 1.87 and 2.26nm, respectively.