Electrochemical doping of mesoporous silicon with Er: the effect of the current intensity

Abstract

• A multidisciplinary approach on porous Si electrochemical Er doping is proposed. • The phenomena taking place at the large developed surface of porous silicon are studied. • Electrochemical, optical and structural characterizations are used. • The early stages of doping are studied by electrochemical impedance spectroscopy. • The dependence of the final amount of Er deposited on the current intensity and not only on the transferred charge is shown. There is an ongoing intense research for cost-effective Er-doped Si-based light-emitting devices at the 1.5 μm wavelength. The efficient electrochemical Er-doping of porous silicon for this purpose requires a good understanding of the phenomena involved, since those taking place at the pores inner surface control the doping process. However, almost no attention has been given, to date, to the relevant effects of the current intensity onto the doping results. In this work, the effect of the current intensity on the doping process is explored by means of electrochemical impedance spectroscopy, optical reflectivity and energy dispersive spectrometry via scanning electron microscopy. The combined analysis of all results strongly suggests that the formation of a gel-like Er ethanolate, unaffected by changes in the sample thickness, occurs from the very first stages of the doping process. Moreover, while for constant current doping processes we show that, under any given doping condition, the doping level is proportional to the transferred charge, we demonstrate that performing the doping process using different current intensities may lead to dramatically different results.