Light Emission from Highly-Strained Germanium for On-Chip Optical Interconnects

In this paper, we focus on developing an efficient silicon-compatible light emitter based on highly-strained germanium technology. We present various experimental results showing enhanced light emission from strained germanium. First, we describe a thin film membrane technique in which a large residual stress in a tungsten layer is used to induce a biaxial tensile strain in germanium membranes. Second, we introduce an approach to induce sufficiently large uniaxial strain to create a direct band gap in germanium (Ge) nanowires using geometrical amplification of a small pre-existing strain. Lastly, we present a novel way to mimic double-heterostructure behavior within a single material, further enhancing light emission from Ge by capturing photo-generated carriers in a strain-induced potential well. Throughout this paper we discuss the implications of these experimental achievements toward creating an efficient Ge laser for silicon-compatible optical interconnects.