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Inductively coupled plasma dry etching for the fabrication of fine-pitch patterns in a wide range of InP-based materials has been developed. The effect of plasma chemistry (the N2 content in the total Cl2/Ar/N2 gas mixture) on the degree of undercut in the sidewall profile and surface morphology has been studied. Optimization of the etch process conditions produces strong passivation effects on the sidewalls, together with a highly anisotropic process, while still maintaining a good etch rate (560–730 nm/min). Single-step etching using hydrogen silsesquioxane as a resist/hard-mask resulted in high aspect ratio features being obtained (up to 30:1). Low plasma excitation power (inductively coupled plasma machine operating power of 400 W) and moderate ion energy (rf power of 120 W) were utilized to minimize etch-induced damage and provide low scattering losses. Low-loss (<0.3 dB/mm) optical ridge waveguides and high reflectivity and high-wavelength selectivity (Δλ=2 nm) results with 236 nm period sidewall gratings were demonstrated experimentally. [ABSTRACT FROM AUTHOR]

Optimized fabrication of submicron-sized features in gallium nitride (GaN) with the use of inductively coupled plasma (ICP) dry etching, based on SiCl4/Cl2/Ar gas mixture, is presented. Dense periodic patterns, i.e., 400-nm-period gratings, were transferred into a gallium nitride waveguide under different etching conditions. ICP power, radiofrequency (RF) power, chamber pressure, and Ar/Cl2 gas mixing ratio were altered during the experiment. Depths of fabricated grating couplers up to 670 nm were achieved. The most suitable etching conditions are discussed with the assessment based on etching selectivity, scanning electron microscopy (SEM) observation of grating tooth slope, hard-mask erosion process, and etched surface morphology. [ABSTRACT FROM AUTHOR]

Polymer hydrogen silsesquioxane (HSQ) solution in methyl isobutyl ketone (MIBK) commercially known as FOx (flowable oxide) is an alternative material to silicon dioxide obtained by chemical deposition. Standard process to obtain amorphous SiO2 film from polymer HSQ includes: deposition by spin coating, removal of solvent by softbake on hotplate and oxidation of materials by heating in an oven or oxygen plasma treatment. Having parameters similar to those of SiO2, polymer HSQ after softbake is sensitive to an electron beam and also to wavelengths below λ 157 nm. Due to those factors, it can be used as a high resolution (20 nm details) negative mask in next generation lithography and in e-beam lithography. Removal of FOx after hardbake is possible only with dry etching or in HF solution. The paper reports on possibilities of application of HSQ polymer for integrated optoelectronics. Technology of obtaining an SiO2 layer from HSQ polymer is described. Measurements of thickness, refractive index and transmittance from 200 nm to 800 nm are reported for the fabricated layers. [ABSTRACT FROM AUTHOR]

We measured the absorption recovery times in reverse biased AlInGaAs multiple quantum well material designed to emit at around 1.5 μm wavelength. Absorption recovery times as low as 2.5 ps were found at -4V bias, with values below 5 ps consistently found for biases above 3 V. The short absorption recovery times obtained under reverse bias were confirmed by using cross-absorption modulation in the material to demonstrate wavelength conversion of a 10 GHz pulse train, showing both up and down conversion of the incident pulses., (© 2011 Optical Society of America)

We describe a new technique for random surface texturing of a gallium nitride (GaN) light-emitting diode wafer through a mask-less dry etch process. This involves depositing a sub-monolayer film of silica nanospheres (typical diameter of 200 nm) and then subjecting the coated wafer to a dry etch process with enhanced physical bombardment. The silica spheres acting as nanotargets get sputtered and silica fragments are randomly deposited on the GaN epi-layer. Subsequently, the reactive component of the dry etch plasma etches through the exposed GaN surface. Silica fragments act as nanoparticles, locally masking the underlying GaN. The etch rate is much reduced at these sites and consequently a rough topography develops. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) inspections show that random topographic features at the scale of a few tens of nanometres are formed. Optical measurements using angle-resolved photoluminescence show that GaN light-emitting diode material thus roughened has the capability to extract more light from within the epilayers.

We characterized the reflectivity and the modal discrimination of intracavity reflectors (ICRs) with different numbers of slots and presented harmonic mode-locking operation of a monolithic semiconductor laser comprising a compound cavity formed by a single deeply etched slot ICR fabricated from 1.55 μm AlGaInAs strained quantum well material. Gaussian pulses were generated at a 161.8 GHz repetition rate with a pulse duration of 1.67 ps and a time-bandwidth product of 0.81.

At higher frequencies (visible and infrared) both the dimensions and the individual metal properties play an important role in determining the resonant response of arrays of SRRs. As a result, a substantial difference between the responses of gold- and Al-based SRR arrays has been observed. Additionally, deposition of gold SRRs onto a substrate typically involves the use of an additional adhesion layer. Titanium (Ti) is the most common adhesive thin-film material used to attach gold onto dielectric/semiconductor substrates. In this paper we investigate the impact of the Ti adhesion layer on the overall response of Au-based nano-scale SRRs. The results quantify the extent to which the overall difference in the resonance frequencies between Au- and Al-based SRRs is due to the presence of the Ti. We show that even a 2-nm-thick Ti layer can red-shift the position of SRR resonance by 20 nm. Finally, we demonstrate that by intentional addition of titanium in the Au-based SRRs, their overall resonant response can be tuned widely in frequency, but at the expense of resonance magnitude.