S. Guilet

Sidewall passivation assisted by a silicon coverplate during Cl2–H2 and HBr inductively coupled plasma etching of InP for photonic devices

Energy dispersive x-ray (EDX) spectroscopy coupled to transmission electron microscopy (TEM) is used to analyze the passivation layer deposited on the sidewall of InP submicron patterns etched in Cl2–H2 and HBr inductively coupled plasmas. It is shown that a thin Si-containing layer is deposited on the sidewalls of the etched patterns, resulting from the reaction of Cl2 or HBr with the Si wafer used as the sample tray. For Cl2-containing plasma, the deposition layer becomes thicker when hydrogen is added to the gas mixture, leading to highly anisotropic InP etching at an optimized H2 percentage. A similar effect is obtained in HBr plasma by increasing the ICP power. When O2 is added to the gas mixture, the deposited layer is changed from Si rich to more stoichiometric silicon oxide (SiO2) and the passivation effect is enhanced. EDX-TEM analysis has also been carried out on InP samples etched in Cl2–N2 plasma for comparison. A similar impact of the coverplate material on the sidewall profile is evidenced, ...

Continuous-wave operation of photonic band-edge laser near 1.55 μm on silicon wafer

We report on the continuous-wave operation of a band edge laser at room temperature near 1.55 μm in an InGaAs/InP photonic crystal. A flat dispersion band-edge photonic mode is used for surface normal operation. The photonic crystal slab is integrated onto a Silicon chip by means of Au/In bonding technology, which combines two advantages, efficient heat sinking and broad band reflectivity.

Optimization of a Cl2–H2 inductively coupled plasma etching process adapted to nonthermalized InP wafers for the realization of deep ridge heterostructures

Inductively coupled plasma etching using Cl2–H2 chemistry with no additive gas (CH4, Ar, or N2) is studied to realize deep (>5μm) ridges with smooth and vertical sidewalls. The process is optimized for nonthermalized InP wafers to avoid the use of thermal grease. Cleaning of the rear side of the wafer after etching is avoided, which is suitable for an industrial process or for critical subsequent steps such as epitaxial regrowth. The influence of the Cl2∕H2 ratio on the etching mechanism is investigated for both InP bulk layers and InGaAs∕InP or InGaAlAs∕InP heterostructures. The authors show that this ratio is the main parameter controlling the ridge profile, in a similar way for both bulk InP and InGa(Al)As∕InP samples. Smooth and vertical sidewalls with neither undercuts nor notches can be obtained in the 0.5–1mT pressure range for a hydrogen percentage of 35%–45% in the gas mixture. Etching rates from 900to1300nm∕min together with a selectivity over SiNx dielectric mask as high as 24:1–29:1 are measur...

Surface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurements

A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125–500 s−1 range (γH surface recombination coefficient of ∼0.006–0.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of...

Development of ion sources from ionic liquids for microfabrication

In this article the authors present the potential of ionic liquid ion sources (ILISs) for direct microfabrication of silicon structures. The authors have developed a specific source geometry using the ionic liquid EMI-BF4 to obtain stable emission currents up to the 10 μA regime. ILIS (EMI-BF4) engraving properties were then investigated. The results and the chemical analysis of the patterned substrates suggest that reactive ion species can be generated from ILIS. This possibility is of major interest to allow decisive advances in the field of focused ion beam applications.

Smooth sidewall in InP-based photonic crystal membrane etched by N2-based inductively coupled plasma

The etching for InP photonic crystal (PhC) hole structure using Cl2∕BCl3∕N2 and BCl3∕N2 inductively coupled plasmas has been investigated for the fabrication of membrane devices. The addition of N2 into Cl2-based plasma is shown to enhance the anisotropic etching and to suppress the sidewall roughness compared to the Cl2∕Ar plasma. The profile verticality of PhC structures is improved by the introduction of BCl3. The smooth sidewalls and the vertical hole profiles are obtained when N2 ratio (N2 mass flow rate/total gas flow) is superior to 65%. Positive ion fluxes are measured with the variations of gas flow rates for the plasma characterization. It is found that the addition of N2 to the Cl2∕BCl3 plasma can cause a decrease in positive ion density when the N2 ratio is more than 20%. Chemical identification of the InP surface after etching by a N2-based plasma is characterized by transmission electron microscopy, and no nitrogen element is observed along the sidewalls, which indicates a low probability of...

Anisotropic and Smooth Inductively Coupled Plasma Etching of III-V Laser Waveguides Using HBr- O2 Chemistry

HBr inductively coupled plasma (ICP) etching is investigated to realize ridge laser waveguides on InP and GaAs substrates. It has been reported that pure HBr chemistry leads to undercut ridge profiles when a hard dielectric mask is used. In this paper we show that a passivation layer can build up on the sidewalls and prevent lateral etching at high ICP powers if a Si wafer is used as the sample tray. Ex situ energy-dispersive X-ray analysis coupled to transmission electron microscopy shows that the passivation layer is a Si-rich silicon oxide. Vertical sidewalls, a smooth etched surface, and a moderate etch rate compatible with the processing of shallow ridge lasers can be obtained for InP-based heterostructures. The optimized HBr etching process is used to etch InAs quantum dot shallow ridge lasers grown on InP(100) substrate and compared to a classical HCl selective chemical etch. The waveguide losses of the HBr-etched waveguide do not differ from those of the chemically etched waveguide by more than 1 cm -1 . Finally, we show that a similar passivation mechanism can be obtained during HBr ICP etching of GaAs/AlGaAs ridge waveguides, demonstrating that the same HBr (-O 2 ) chemistry is suitable for both GaAs and InP systems.

Efficient coupling to W1 photonic crystal waveguide on InP membrane through suspended access guides

Suspended access ridges have been designed and integrated with a single-missing row photonic crystal guide on InP membrane in order to improve the coupling efficiency. This integration provides control of the injection into the photonic crystal (PhC) guide and a deterministic choice of the termination of the PhC. Low propagation losses have been measured for both the photonic crystal guide on InP membrane and the suspended ridges.

Investigation of InP etching mechanisms in a Cl2/H2 inductively coupled plasma by optical emission spectroscopy

Optical emission spectroscopy (OES) has been used in order to investigate the InP etching mechanisms in a Cl2–H2 inductively coupled plasma. The authors have previously shown that anisotropic etching of InP could be achieved for a H2 percentage in the 35%–45% range where the InP etch rate also presents a local maximum [J. Vac. Sci. Technol. B 24, 2381 (2006)], and that anisotropic etching was due to an enhanced passivation of the etched sidewalls by a silicon oxide layer [J. Vac. Sci. Technol. B 26, 666 (2008)]. In this work, it is shown that this etching behavior is related to a maximum in the H atom concentration in the plasma. The possible enhancement of the sidewall passivation process in the presence of H is investigated by comparing OES measurements and etching results obtained for Cl2–H2 and Cl2–Ar gas mixtures.

Impact of the GaN nanowire polarity on energy harvesting

We investigate the piezoelectric generation properties of GaN nanowires (NWs) by atomic force microscopy equipped with a Resiscope module for electrical measurements. By correlating the topography profile of the NWs with the recorded voltage peaks generated by these nanostructures in response to their deformation, we demonstrate the influence of their polarity on the rectifying behavior of the Schottky diode formed between the NWs and the electrode of measurement. These results establish that the piezo-generation mechanism crucially depends on the structural characteristics of the NWs.