Spectrally-shaped illumination for improved optical inspection of lateral III-V-semiconductor oxidation.

We report an hyperspectral imaging microscopy system based on a spectrally-shaped illumination and its use to offer an enhanced in-situ inspection of a technological process that is critical in Vertical-Cavity Surface-Emitting Laser (VCSEL) manufacturing, the lateral III-V-semiconductor oxidation (AlOx). The implemented illumination source exploits a digital micromirror device (DMD) to arbitrarily tailor its emission spectrum. When combined to an imager, this source is shown to provide an additional ability to detect minute surface reflectance contrasts on any VCSEL or AlOx-based photonic structure and, in turn, to offer improved in-situ inspection of the oxide aperture shapes and dimensions down to the best-achievable optical resolution. The demonstrated technique is very versatile and could be readily extended to the real-time monitoring of oxidation or other semiconductor technological processes as soon as they rely on a real-time yet accurate measurement of spatio-spectral (reflectance) maps.

Scanning microwave microscopy applied to semiconducting GaAs structures.

A calibration algorithm based on one-port vector network analyzer (VNA) calibration for scanning microwave microscopes (SMMs) is presented and used to extract quantitative carrier densities from a semiconducting n-doped GaAs multilayer sample. This robust and versatile algorithm is instrument and frequency independent, as we demonstrate by analyzing experimental data from two different, cantilever- and tuning fork-based, microscope setups operating in a wide frequency range up to 27.5 GHz. To benchmark the SMM results, comparison with secondary ion mass spectrometry is undertaken. Furthermore, we show SMM data on a GaAs p-n junction distinguishing p- and n-doped layers.

Low-loss buried AlGaAs/AlOx waveguides using a quasi-planar process.

In this paper, we demonstrate that buried oxide-confined waveguides can be formed using a lateral oxidation process carried out through a discrete set of small-diameter via-holes instead of the conventional scheme where the oxidation starts from the edges of etched mesas. The via-hole oxidation is shown to lead to straight waveguides with smooth oxide/semiconductor interfaces and whose propagation losses are similar to one obtained using the standard process but with the advantage of maintaining a quasi-planar wafer surface. It thereby paves the way towards a simplification of the fabrication of III-V-semiconductor-oxide photonic devices.