Showing papers by "Vincent Aimez published in 2002"

Low-energy ion-implantation-induced quantum-well intermixing

Abstract: In this paper, we present the attractive characteristics of low-energy ion-implantation-induced quantum-well intermixing of InP-based heterostructures. We demonstrate that this method can fulfil a list of requirements related to the fabrication of complex optoelectronic devices with a spatial control of the bandgap profile. First, we have fabricated high-quality discrete blueshifted laser diodes to verify the capability of low-energy ion implantation for the controlled modification of bandgap profiles in the absence of thermal shift. Based on this result, intracavity electroabsorption modulators monolithically integrated with laser devices were fabricated, for the first time, using this postgrowth technique. We have also fabricated monolithic six-channel multiple-wavelength laser diode chips using a novel one-step ion implantation masking process. Finally, we also present the results obtained with very low-energy (below 20 keV) ion implantation for the development of one-dimensional and zero-dimensional quantum confined structures.

A novel fabrication technique for multiple-wavelength photonic-integrated devices in InGaAs-InGaAsP laser heterostructures

Abstract: We report the fabrication of multiple wavelength chips in InGaAs-InGaAsP laser structure using a novel ion implantation induced quantum-well (QW) intermixing technique. This technique first consists of using a gray mask photolithography and reactive ion etching process to create a SiO/sub 2/ implant mask with variable thickness on the sample. This is followed by a single 360-keV phosphorus ion implantation at a dose of 1/spl times/10/sup 14/ cm/sup -2/ at 200/spl deg/C, which creates different amounts of point defects in the sample depending on the local thickness of the SiO/sub 2/ mask. A subsequent thermal annealing step induces QW intermixing through the diffusion of the point defects across the structure. With this technique, we have successfully fabricated 10-channel multiple wavelength laser diodes, with lasing wavelength spreading over 85 nm (between 1.47 and 1.55 /spl mu/m), monolithically integrated on a single chip. Only a limited increase of threshold current density of 17% (i.e., from 1.2 to 1.4 kA/cm/sup 2/), has been observed between the least intermixed and the most intermixed lasers.

Generation of Multiple Energy Bandgaps Using a Gray Mask Process and Quantum Well Intermixing

Abstract: We report a technique for generation of multiple energy bandgaps using a combination of one-step gray mask lithography and low-energy arsenic ion implantation induced disordering. Using this technique, we have successfully integrated 12-section with variable energy bandgaps on a single InGaAs/InGaAsP laser heterostructure. When compared to conventional processes, this novel technique is simple, promising and cost effective.

Monolithic multiple wavelength ridge waveguide laser array fabricated by Nd:YAG laser-induced quantum well intermixing

Abstract: Maskless selective area cw Nd:YAG laser annealing of GaInAsP/InP quantum well (QW) structures has been investigated as a possible route towards the fabrication of monolithically integrated photonic circuits. Laser irradiation of a 5 QW laser structure, originally designed for lasers emitting at 1.52 μm, yielded material having a continuously changing band gap ranging from 1.52 to 1.4 μm over the distance of about 3 mm. Bars with arrays of ridge waveguide lasers, having cavity lengths from 300 to 600 μm, were fabricated from the processed material. An individual bar, 2–3 mm long, comprised lasers operating typically between 1.4 and 1.52 μm. The lasers showed stable threshold current density and high quantum efficiency at all operating wavelengths. The results indicate that the applied approach has the potential to realize the cost-effective fabrication of advanced photonic devices and photonic integrated circuits.

Analysis of strain-induced polarisation-insensitive integrated waveguides fabricated using ion-implantation-induced intermixing

Abstract: The interdiffusion effect on the strain build-up and refractive index profile of lattice-matched InGaAs/InGaAsP multiple quantum wells is reported. Interdiffusion is achieved experimentally using low energy (360 keV) arsenic or phosphorus ion-implantation-induced disordering, followed by an annealing step. A model of the interdiffusion process has been developed to analyse the effect of different interdiffusion ratios on the waveguide's polarisation behaviour through the strain build-up and the refractive index profiles for the transverse electric and transverse magnetic modes. Polarisation-resolved photocurrent absorption measurements of quantum-well waveguide structures have shown that sufficiently high ion implantation doses can lead to the realisation of polarisation-insensitive waveguides at 1.55 /spl mu/m wavelength operation. Comparison with the modelling results shows that the polarisation-dependent behaviour of the waveguides is best described by a higher interdiffusion ratio for the group V than for the group III atoms.

Magneto–photoluminescence study of intermixed self-assembled InAs/GaAs quantum dots

Abstract: The electronic structure of InAs/GaAs self-assembled quantum dots and the carrier capture dynamics in these dots have been studied by magneto–photoluminescence at low temperature (5 K). We report results obtained on a series of samples processed by rapid thermal annealing. This intermixing procedure led to a significant narrowing of the inhomogeneous photoluminescence emission bands related to the various dot shell states, as compared to results obtained on unprocessed samples, which in turn improved the conditions for the observation of the Fock–Darwin energy levels structure as a function of the magnetic field, up to 15 T. We also observed that the ratio of the wetting layer emission intensity over the integrated intensity of the quantum dot emission bands increases nonlinearly with the magnetic field. This nonlinear behavior, which is more apparent at low photocarrier density, suggests that transport properties contribute to limit the carrier capture by the dots.

Multiple-wavelength operation of electroabsorption intensity modulator array fabricated using the one-step quantum well intermixing process

Abstract: Multiple-wavelength selective channel electroabsorption intensity modulators have been fabricated on a single InGaAs/InGaAsP chip using a one-step quantum well intermixing process. This technique was demonstrated for tailoring the intensity modulator operating wavelength by incorporating low-energy (360 keV) phosphorus ions implantation induced disordering process with gray-mask lithography technology. A modulation depth of −15 dB has been measured from these devices with a voltage swing of −4.5 V.

Polarisation insensitive InGaAs/InGaAsP electro-absorption intensity modulator using quantum well intermixing process

Abstract: A quantum well intermixing process for the fabrication of polarisation insensitive electro-absorption intensity modulators on an InGaAs/InGaAsP heterostructure is reported. This technique is based on low-energy arsenic and phosphorus ion implantation.

Development of a spatially selective, high resolution quantum well intermixing (HRQWI) method based on low energy ion implantation

Abstract: Summary form only given. In order to develop a high resolution quantum well intermixing process (HRQWI), using partially grown heterostructures, where the active region is situated at shallow depth, there is a list of requirements that have to be fulfilled : the bandgap increase has to be sufficiently high to obtain quantum confinement; the high quality optical characteristics of the material have to be conserved; the surface morphological quality of the material following HRQWI has to remain very high in order to allow the regrowth of upper cladding layers; and the spatial resolution of the process has to be on the order of 100 nm. The results presented here fulfil the first three requirements while allowing further work to be carried out in order to assess the fourth requirement.