Abstract
Erbium, a rare earth element, has been shown to exhibit characteristic luminescence at 1.54mum due to its internal 4f transition from the first excited state (4pi3/2) to the ground state (4pi5/2). As this emission wavelength falls inside the maximum transmission window of silicon based optical fibers, erbium doped silicon might lead to the opportunity of silicon based optoelectronics. The introduction of erbium in silicon allows excitation through electron-hole recombination and subsequent radiative emission from the rare earth centers. The works reported here describe the structural, electrical and optical properties of crystalline silicon codoped with erbium and boron by ion implantation technique. Four sets of samples, co-implanted with erbium and boron at different Er dose, implantation energy and at different conditions, were prepared. Post-implantation annealing has been performed to recover the implantation damage to an acceptable value and to activate the dopant atoms optically and electrically. PL and EL measurements have been performed in the temperature range between 80K to room temperature. The sample with the lowest erbium concentration and energy gives the best PL and EL results. The observed emission peaks in both PL and EL measurements were at around 1.129mum, ~1.303mum, 1.50mum and 1.597mum at 80K. At higher temperatures, a broader peak at around 1.50mum with long tail towards the both end of wavelength has been observed. The peak at 1.129mum corresponding to the Si band edge emission, the reason for the peaks at around l.303mum has not been identified while the remaining two peaks correspond the Er3+ emission. Virtually no temperature quenching of Er luminescence is observed in some samples rather room temperature intensity is higher than that at 80K. The improvement of the temperature quenching effect on Er luminescence at room temperature has been attained in our results, which is significant improvement in comparison to the result found in the literature. The structural properties were studied by TEM in both cross-sectional and plan view configurations. TEM analyses showed dislocation loops and other defects of random size and distribution from the surface to 600nm below the surface. Er precipitates defects were also seen in the sample doped with Er comparatively at higher dose (1x1015Er/cm2) and energy (1.0 MeV). No detectable room temperature PL and EL signals were observed from the sample implanted at higher doses and energies.