Optical properties of thin-film silicon-compatible materials

Abstract

The optical performance of photodetectors in silicon strongly depends on the transmission of incident light into Si and the charge collection efficiency therein. Consequently, improving the transmission efficiency of light into Si by means of an interference antireflectant (AR) filter can lead to improved optoelectric conversion efficiency. However, the design of these filters requires the availability of data on the optical characteristics of the materials used. Furthermore, for the realization of such filters for light detectors realized in silicon, the required compatibility with standard microelectronic processing implies that only Si-compatible materials should be used. The range of such Si-compatible materials available for fabricating photoelectric devices in silicon includes thermally grown SiO(2), low-pressure chemical-vapor deposited polysilicon, silicon nitride (low stress and stoichiometric), and oxides (low-temperature oxide, phosphosilicate glass, borosilicate glass, borophosphosilicate glass) as well as plasma-enhanced chemical-vapor deposited oxynitrides. We present the refractive index and the extinction coefficient of these materials in the 380-800-nm range. The data presented enhance the accuracy and applicability of simulation and design tools used to design photodetectors in silicon for the visible range.