During the fabrication of metal oxide semiconductor high electron mobility transistor based on AlGaN/GaN heterostructure, gate patterning is recognized as the most critical step that can lead to electrical degradation of the transistor. In this work, we performed the SiN cap layer plasma etching processes by two fluorine-based plasma processes (SF6/Ar and CHF3/CF4/Ar) with low (≈15 eV) and high (≈260 eV) ion energies. Moreover, we investigate the postetching treatment using a KOH solution in order to restore the quality of the AlGaN barrier surface after etching. The objective of this article is to evaluate the AlGaN barrier surface damage after the listed plasma etching processes and postetching strategies by using quasi-in situ angle-resolved x-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscope. Accordingly, it is found that both high ion energy plasma processes lead to a significant stoichiometric change and modification of the AlGaN barrier layer into a 1.5 nm F-rich AlGaNFx subsurface reactive layer. The decrease in ionic energy leads to a decrease in the SiN etch rate and a significant improvement in the SiN/AlGaN etch selectivity (which becomes infinite) for both plasma chemistries. Moreover, the decrease in ion energy decreases the depth of the modification (about 0.5 nm) and reduces the stochiometric change of the AlGaN barrier layer. However, both low and high ion energy SF6/Ar plasma lead to 0.8 eV Fermi level shift toward the valence band. Furthermore, the KOH postetching treatment demonstrates complete and effective removal of the AlGaNFx subsurface reactive layer and restoration of the surface properties of the AlGaN layer. However, this removal leads to AlGaN recesses that are correlated to the thickness of the reactive layer formed during the etching.

A high brightness silicon integrated source of entangled frequency-bins is presented. We experimentally demonstrate programmable emission of both computational basis states and Bell states.

Two low-damage plasma etching processes have been investigated to evaluate their impact on the integrity of the AlGaN layer during the SiN gate opening process of Metal Insulator Semiconductor High Electron Mobility Transistors (MIS-HEMT). We show that the low ion energy fluorocarbon plasma presents an infinite SiN/AlGaN etch selectivity despite significant surface modifications. In contrast, the smart etch process, that alternates H 2 plasma-based surface modification with chemical removal of the modified surface, preserves the surface of AlGaN. However it can lead to AlGaN recess due to over-implantation during the H 2 plasma step. Finally, we show that a KOH post etchi treatment removes plasma-induced damages. Therefore, combining the smart etch process with a KOH post etch treatment offers an interesting solution for SiN patterning over AlGaN with minimized surface modification and restored AlGaN surface quality.

We present a highly-efficient integrated reconfigurable source of entangled frequency bins. Leveraging the flexibility offered by the silicon photonics platform, we demonstrate the on-chip generation of all the main two-qubit quantum states.

We demonstrate spontaneous four-wave mixing in two linearly uncoupled resonators employing a Mach-Zehnder interferometer capable of wide band (>150 nm) operation and a fourfold improvement in the generation rate with respect to previous configurations.

Controlling the plasma etching step involved in metal-oxide-semiconductor high-electron-mobility-transistor (MOSHEMT) GaN fabrication is essential for device performance and reliability. In particular, understanding the impact of GaN etching conditions on dielectric/GaN interface chemical properties is critically important. In this work, we investigate the impact of the carrier wafers (Si, photoresist, SiO2, and Si3N4) used during the etching of GaN in chlorine plasma on the electrical behavior of Al2O3/n-GaN metal–oxide–semiconductor (MOS) capacitors. X-ray Photoelectron spectroscopy (XPS) analyses show that the Al2O3/GaN interface layer contains contaminants from the etching process after the Al2O3 deposition. Their chemical nature depends on the plasma chemistry used as well as the chemical nature of the carrier wafer. Typically, Cl and C are trapped at the interface for all substrates. In the particular case of Si carrier wafer, a significant amount of SiOx is present at the Al2O3/GaN interface. The capacitance–voltage (C–V) characteristics of the MOS capacitors indicate that the presence of Si residues at the interface shifts the flat band voltage to negative values, while the presence of Cl or C at the interface increases the hysteresis. We demonstrate that introducing an in situ plasma cleaning treatment based on N2/H2 gas, before the atomic layer deposition, allows the removal of most of the residues except silicon and suppresses the hysteresis.

Dissipative Kerr solitons in microresonators enable on-chip chip generation of low-noise optical pulse trains with high repetition rates, finding applications in optical communication, distance measurement, spectroscopy and radiofrequency generation. However, the most common photonic integrated platforms often show very short living, hence difficult to achieve, soliton states. Here, we exploit an auxiliary resonance to access soliton regime in Si3N4 microresonators by simple wavelength scanning. We increase the likelihood of single soliton formation by more than two times using backward tuning of the laser, and we show that the increased thermal stability allows soliton formation by thermal tuning of the whole sample, keeping the laser at a fixed frequency.

We exploit orthogonally polarized resonant modes to achieve thermal equilibrium for Kerr soliton generation in Si3N4 microrings. The improved thermal stability allows for soliton mode-locking simply by slow wavelength tuning or thermoelectric cooling.

We report on the suppression of nonlinear parasitic processes affecting dual-pump spontaneous four-wave mixing in ring resonators. We measure an enhancement of over 104 in the signal-to-noise ratio with respect to conventional ring resonators.

Ridge microstructures were prepared by reactive ion etching (RIE) of a series of stacked InAsxP1-x quantum wells (QWs) with step graded compositions grown on InP by molecular beam epitaxy. These microstructures were characterized by low temperature micro-photoluminescence. The photoluminescence (PL) emission associated with each of the QWs was clearly identified and a model for their line shape was implemented. PL line-scans were measured across etched ridge stripes of various widths in an optical cryostat, with a spatial resolution of 1 mu m. The model for the PL spectra allowed accurate extraction of the local PL integrated intensities, spectral positions and line widths. Two different RIE processes, using CH4/H-2 and CH4/Cl-2, were investigated. The PL line-scans showed strong variations of the integrated PL intensities across the etched stripes. The PL intensities for all QWs increased gradually from the edge to the center of the ridge microstructures, over a length scale of 10-20 mu m. On the other hand, the spectral peak position of the PL lines remained constant (within an accuracy of 0.2-0.4 meV, depending on which QW was considered) across the microstructures. These observations are discussed in terms of the mechanical stress induced by the RIE processes, the relaxation of the biaxial built-in compressive stress in the InAsP QWs (induced by the free surfaces at the vertical etched sidewalls), and also by the non-radiative recombination at these sidewalls. Altogether, this study illustrates the contribution that specially designed test structures, coupled with advanced spectroscopic characterization, can provide to the development of semiconductor photonic devices (e.g. lasers or waveguides) involving RIE processing.

We report on the generation of photon pairs through dual-pump four-wave-mixing in a system composed of two resonators coupled solely through a third-order nonlinear interaction, which allows for the suppression of parasitic nonlinear phenomena.

Microelectronic processing to fabricate electronic devices on Si has been extensively studied and well characterized for several decades. This type of processing has been extrapolated for the fabrication of devices on other semiconducting materials such as group III–V materials, SiGe and SiC. However, the structural damage and its functional implication are still not fully understood for sensitive materials like InP. The present work investigates the lattice strain induced by the inductively coupled plasma dry etching process on InP stripes fabricated after masking the stripes with plasma-enhanced chemical vapor deposition-grown SiNx. High-resolution scanning transmission electron microscopy observations allowed us to deduce the strain at different locations in the fabricated stripes. Local strains in the range of 10−3 are observed, which should strongly modify the material carrier behaviour.

We exhibit the generation of soliton microcombs with 1.48-THz line spacing over 8.8 THz around 1575 nm by using the self-injection locking of a III-V DFB laser butt-coupled to a Si3N4 microresonator.