High‐Pressure Chemical Deposition for Void‐Free Filling of Extreme Aspect Ratio Templates

Abstract

Extreme aspect ratio semiconductor structures are critical to modern optoelectronic technology because of their ability to waveguide light and transport electrons. Waveguides formed from almost any material by conventional micro/nanofabrication techniques typically have significant surface roughness that scatters light and is a constraining factor in most optoelectronic devices. For example, fabricated planar silica waveguides have optical losses 3 to 5 orders of magnitude higher than silica fibers, in part due to surface roughness. For these reasons silica nanofibers have been proposed as alternatives to fabricated silica or semiconductor channels for waveguiding of light in miniaturized optical devices, as they meet the strict requirements for surface roughness and diameter uniformity required for low loss. An additional advantage of these silica fibers is that they have a circular cross section that can simultaneously guide both transverse electric (TE) and transverse magnetic (TM) polarizations without cutoff. In contrast the rectilinear cross sections of microfabricated planar waveguides can effectively guide only one polarization without cutoff. However, semiconductors in general exhibit a far broader range of useful optoelectronic function than silica glass because of their ability to form hetero and homojunctions, serve as optical gain media over a broad range of wavelengths, and their superior non-linear optical properties.