Abstract
The luminescence properties of erbium-doped silicon with fluorine as a codopant have been studied. Erbium in silicon is seen as a very promising way to obtain light emission from silicon. With the aim of improving understanding of the role of fluorine in the Er:Si system, erbium and fluorine were implanted into silicon substrates and annealing was carried out to regrow the damaged silicon. The material properties were studied using Rutherford backscattering spectrometry and correlated with the luminescence properties, which were investigated using photoluminescence spectroscopy. Frequency resolved photoluminescence spectroscopy was used to provide information on the lifetimes associated with the luminescence process. This is the first time this technique has been applied to this system. Erbium has been incorporated in good quality crystal Si at concentrations up to 1020 cm-3. This is two orders of magnitude greater than the estimated solid solubility and equals the highest reported concentration for erbium in crystalline Si. For all but the highest fluorine dose employed, regrowth of the silicon took place to at least within 250 A of the surface. Fluorine doses of 5x1016 cm-2 appeared to disrupt the epitaxial regrowth of the silicon and very weak photoluminescence was obtained. At the lowest fluorine dose employed (1015 cm-2) segregation of the erbium occurred into two regions consistent with the formation of a buried amorphous layer following the original implants. In high resolution photoluminescence spectra, lines were observed which have been identified as due to isolated interstitial erbium. A thermally unstable interstitial lattice site of hexagonal symmetry was also identified, as well as lines originating from implantation related defects. All the samples exhibited luminescence whose decay could be represented by two lifetimes, both of which were strong inverse functions of temperature, and whose values at 75 K were approximately 200 mus and 700mus. An idea for a temperature sensor is presented which could be realised using current implant technology.