Use of amorphous silicon for active photonic devices

Silicon photonics is a new emerging and disruptive technology aimed at using cost-effective silicon-based materials for the generation, control, and detection of modulated light signals for optical communication. Hydrogenated amorphous silicon (a-Si:H) is a particularly promising platform for enabling the desired matching between electronics and on-chip photonics. Thin a-Si:H layers can be in fact deposited using the CMOS-compatible low-temperature plasma-enhanced chemical vapor deposition technique, with no impact at all on the microelectronic layers. This paper provides an overview of the progress and the state of the art of a-Si:H-based active photonic devices, focusing, in particular, on the low technological complexity required for an easy integration within a single photonic microchip. This paper consists of three main sections, in each of which the exploitable optoelectronic effects present in a-Si:H are presented. A comparison between some experimental a-Si:H and crystalline-Si photonic components available in the literature is presented.