F. Vermaerke

Anisotropic photoluminescence behaviour of vertical AlGaAs structures grown on gratings

Abstract The formation of vertical AlGaAs quantum wells during MOVPE growth of AlGaAs layers on submicron gratings has been investigated. The influence of the growth temperature, growth velocity, V/III ratio and the overall Al content has been examined and explained using surface diffusion effects of the group III atoms (or reactant species). 77 K PL measurements show a polarization anisotropy and indicate lateral quantum confinement. Also the growth of QWWs on submicron gratings is reported, showing very large PL intensities and polarization anisotropy. Finally the realization of QWWs has been proposed by growing AlxGa1-xAs/AlyGa1-yAs QWs on gratings and based on the different surface mobilities of Ga and Al.

Epitaxial lift-off of ZnSe based II-VI structures

The epitaxial lift‐off technique is applied to II–VI based structures. Epilayers of 255 nm thickness containing quantum wells are lifted off their substrates and redeposited onto polyimide coated GaAs. The technique has also been applied to II–VI samples onto which dielectric films had been deposited. Photoluminescence measurements show that the material quality has not been degraded during the processing. The success of this technique with II–VI’s opens up many possibilities for the integration of these materials with metals and dielectrics in vertical structure devices.

Integration technology for light-source arrays with polymeric optical waveguide arrays

The integration of efficient semiconductor lightsources with low-loss functional optical waveguide devices is one of the major problems in integrated optics. In this paper we present a novel integration scheme based on the epitaxial lift-off technique for the integration of a laser diode array with an array of polymeric waveguides. This method shows a number of advantages with respect to previously reported solutions. The presented quasi-monolithic integration of laser diodes with polymeric waveguides might lead to important applications in areas such as optical interconnections and optical communications.

Improved on-chip lightwave measurements of non-planar optoelectronic devices

In this paper we discuss the difficulties associated with the high-frequency characterization of optoelectronic devices. We present solutions that improve the accuracy of conventional (l) and previously reported (2)-(6) techniques for measuring the high-frequency modulation response of optoelectronic devices. The mathematical expressions necessary for calibration are implemented in the parameter extraction software HP- ICCAP. All the measurement equipment is controlled with this software. Using a non-conventional wafer probe, it is now possible to contact devices with a strong non-planar surface. As a measurement example, we present experimental results for a non-planar, 980 nm strained quantum well laser diode.

Atmospheric and low pressure metalorganic vapor phase epitaxial growth of vertical quantum wells and quantum well wires on submicron gratings

Nonplanar metalorganic vapor phase epitaxial growth on submicron gratings has been studied. Growth conditions have been determined to preserve the grating structure and also to enhance the formation of crescent shaped quantum well wire-like GaAs layers. These growth parameters have been used to grow the layer structure of a quantum well wire (QWW) laser, only needing one growth run. Although there is not yet clear evidence for two-dimensional quantum confinement, this technique offers some interesting perspectives for the realization of QWW lasers.

Monolithic integration of a single quantum well laser diode and a mode-size convertor using shadow-masked metalorganic vapour phase epitaxial growth

Abstract In this paper we propose the monolithic integration of quantum well InGaAs/GaAs 0.98 μm lasers with passive mode-size convertors using the shadow-masked growth technique. The full width at half maximum (FWHM) of the far-field in the transverse direction could be reduced from 47° to 30° without a significant increase of Ith and even a slight increase of νd. Values down to 21° could be reached although a small penalty in threshold current had to be paid. Along the tapered sections, a bandgap increase up to 130 meV has been measured providing transparent windows near the laser facets. Adjusting the nominal layer structure of the laser should allow the realization of reliable 0.98 μm pump lasers for erbium-doped fibre amplifiers showing an improved coupling efficiency in single mode fibres and an enhanced reliability.

Fabrication of Quantum Well Wires and Vertical Quantum Wells on Submicron Gratings by MOVPE

The fabrication of quantum well wires (QWWs) by overgrowing submicron gratings is reviewed. The advantages of one-dimensional semiconductor structures have already been understood for some time and are expected to alter laser performances, such as extremely low threshold currents, very high modulation bandwidths, very low temperature dependence. The realization of the nanostructures, however, has set some major demands on crystal growth. The MOVPE growth on submicron gratings (etched in a GaAs substrate) has become one of the most successful techniques and is studied in this paper. Vertical ‘quantum wells’ (VQWS) (formed during growth of bulk AlxGa1-xAs on gratings) are also studied and a new fabrication technique for QWW lasers is proposed. Finally the application of QWWs and VQWs is discussed for the realization of Fabry-Perot and distributed feedback laser diodes.

Fast and reliable processing of high-performance InGaAs 0.98-μm laser diodes

A simple and highly reliable processing technique for ridge waveguide InGaAs/GaAs SQW lasers is proposed. The comparison is made with other more conventional processing sequences and the measurements indicate that the characteristics of the lasers obtained by this simple method are at least as good and sometimes even better than those made by using the other processing sequences. It also is shown that the simplicity of the process guarantees a high yield. The high performances of these lasers can be further optimized by applying optical coatings.

Emitters for optical interconnection

In order to provide cost effective solutions for different applications in optical interconnection, different approaches are needed. Cost and reliability are important considerations. The wavelength region between 900 nm and 1000 nm is very attractive since cheap Si-detectors can be used, the GaAs substrate is transparent and the fabricated Qw laserdiodes and LEDs have high performances and high reliability. Parallel optical interconnects require high performance (low threshold, high yield), densely packed laser arrays using fiber ribbon. For long distance communication, more emphasis is laid on the power budget and coupling efficiencies. If in parallel optical interconnect the very high modulation speed of laserdiodes is not really needed, InAlGaAs LED-arrays may be used, because of their stability, robustness and the possibility to integrate diffractive lenses on the backside of the component, which makes the component suitable for free-space optical interconnect. The better performances of microcavity LEDs will enhance this option even more.

Basic Growth Studies and Applications of Quantum Structures Grown on Submicron Gratings

The growth on patterned substrates is an interesting way towards the fabrication of low dimensional structures. In this paper we will describe some basic growth studies of Metal Organic Vapour Phase Epitaxy (MOVPE) of GaAs/AlGaAs on V-grooved GaAs substrates and on submicron gratings. The influence of growth temperature, reactor pressure, V/III ratio and growth velocity will be described. From these results it will be shown that high quality crescent shaped quantum wires and vertical quantum wells can be obtained. The applications of these low dimensional structures will be illustrated by the realisation of a novel Distributed Feedback (DFB) laser and by the proposition of an alternative far-infrared intersubband absorption detector.