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We demonstrate a fully integrated polarization beam splitter with a polarization extinction ratio above 25dB for both polarization states and an insertion loss of 2.5dB. The footprint of the device including electrical contacts is 0.4×2mm 2 . A Mach-Zehnder configuration is used, the birefringence in both arms differs due to different waveguide widths. Fabrication tolerances can be compensated with thermal tuning. The device is realized in our generic integration platform, making it viable to provide monolithically integrated solutions for polarization diversity applications.

Basic development steps towards the molecular beam epitaxy growth of AlGaAs/GaAs microcavity structures are presented, which contain self-organized InAs/GaInAs quantum dots as the active medium. The emission wavelength of these structures can be controllably adjusted within 1260–1340 nm by variation of the deposition parameters of the epitaxial layers without the use of any real-time monitoring technique. Based on quantum dot active material with optimized optical emission properties and accurately calibrated layer thicknesses microcavity light emitting diodes were fabricated. 40 μm diameter devices, as characterized on-wafer, showed narrow electroluminescence spectra (FWHM: 13–26 nm) centered at 1310–1325 nm and narrow circular beam widths of FWHM

AlGaAs/GaAs microcavity structures with InAs/InGaAs quantum dot (QD) active regions were grown by molecular beam epitaxy (MBE) on GaAs substrates and their optical characteristics were studied. Methods for the optimization of optical emission properties of the InAs/InGaAs QDs and accurate calibration of the proper layer thickness are discussed. Microcavity light-emitting diodes (MC-LEDs) with a QD active region demonstrate narrow electroluminescence (EL) spectra (FWHM < 15 nm) accompanied by an output beam divergence of only 17°. The MC-LED emission wavelength can be controllably changed by varying the QD material composition in combination with tuning the optical microcavity.

MBE regrowth on MOVPE grown InP and InGaAsP (1.06 μm) layers was found to demand appropriate surface treatment for not sacrificing epitaxial growth performance. Wet chemical etching using a sulphuric acid based solution as well as surface oxidation using UV light/ozone exposure were found to give very satisfactory and basically equivalent results. Particularly with the quaternary material, both methods prove to be destructive in that a non-neglible amount of material is removed from the surface. The removed thickness tends, however, to be smaller with the UV/ozone based process, an advantage, which becomes especially aparent in the presence of lower band gap InGaAs(P) layers which are strongly attacked by the sulphuric acid etchant.

1480nm InGaAsP large optical cavity broad-area laser diodes were developed and optimized for pulsed operation showing optical output power of >18W at 20°C. Furthermore the μs pulse duration regime was investigated with respect to power saturation and self-heating at elevated operating currents.

Magnetotransport investigations of silicon delta -doped Ga0.47In0.53As layers with different electron densities were performed in tilted magnetic fields up to 12 T. The conduction electrons of the samples showed two-dimensional behaviour determined by the dependence of the Hall coefficient on the tilt angle of the magnetic field. Several populated subbands were identified by the normal and the diamagnetic Shubnikov-de Haas effect. The diamagnetic depopulation features of the samples were explained on the basis of calculations done by Reisinger and Koch for symmetrical potential wells. Whereas no quantum Hall effect could be observed at any of the samples in perpendicular magnetic fields up to 12 T, well developed quantum Hall plateaux occurred at a sample with a low doping level above a certain tilt angle. This was found to be due to the depopulation of the higher subbands by the parallel component of the magnetic field.

A theoretical and experimental comparison of homogeneously doped and δ-doped electron supply regions in AlInAs/GaInAs HEMT structures is presented providing optimized design parameters. The electrical material characteristics in dependence of the doping sheet concentration are assessed. Minimization of the HEMT sheet resistivity is attained by variation of the channel/δ-doping plane separation.

Vertical hybrid integration of photodiodes (PD) and silicon-on-insulator (SOI) waveguides has been investigated. To this end, InP-based planar detectors were used onto which a polymer prism was formed to turn the light beam into the vertical direction. The photodiodes were flip-chip mounted onto a SOI waveguide platform using thermo-compression bonding. Comparable high responsivity of around 0.75 A/W was obtained when light was coupled directly into the prism as well as via a SOI waveguide. The responsivity for SOI integrated PDs was found to depend only to a minor extent on input wavelength and polarization. PD bandwidth of up to 10 GHz was measured. The investigated optical coupling scheme proved to work well also when integrating a PD with an array of ten SOI waveguides which are combined with a star coupler.

In this paper we present the integration of an InP-based photodetector with silicon-on-insulator (SOI) waveguides using thermocompression bonding. A BCB prism integrated on top of the light-sensitive area of a planar detector (PD) chip deflects the light from a 4 μm thick SOI waveguide upward into the flip-chip bonded PD. A trench is etched in front of the SOI waveguide to accommodate prisms with apexes up to 7 μm. Using thermocompression bonding between thin gold pads (~500 nm thickness) deposited on both, SOI and photodetector chips an excellent vertical alignment accuracy of ±100 nm can be achieved, limited only by etching and Au-deposition tolerances. A commercial flip-chip bonder provides a lateral alignment accuracy also in the sub-micron range. Together with a previously developed process for integrating lasers and SOA chips using the same technology, fully functional PICs can now be realized on the SOI platform using thermocompression bonding.

The properties of InGaAsN/GaAs heterostructures with quantum wells on GaAs substrates were studied. The GaAsN layers containing InGaAsN quantum wells with a high (exceeding 1%) nitrogen concentration were obtained. The long-wavelength emission in the InGaAsN quantum wells is obtained in the wavelength range up to 1.32 ?m at room temperature. The effect of the InGaAsN quantum parameters on the optical properties of heterostructures is studied.

A photoreceiver optoelectronic integrated circuit based on InP with a bandwidth of 37 GHz is presented. The receiver consists of a 50 GHz waveguide-integrated photodiode and a distributed amplifier with a bandwidth of 39.5 GHz, which is composed of four high-electron mobility transistors. A system experiment at 40 Gb/s receiving an return-to-zero coded optical input signal is demonstrated, and a good quality of eye pattern is achieved.

The photonic-based telecommunication systems are continuously upgraded to a bit rate of 40 Gbit/s. The demand for faster transmission and the requirement of forward error correction (FEC) in data traffic makes it necessary to further extend the bit rate per channel. One of the key elements to fulfil these demands are high-speed photoreceivers in present and in future optical communication systems. Additional functionalities and cost effective packaging, obtained by a high degree of integration, as well as an increased efficiency and ease of use of the components are mandatory. The InP-based integrated photoreceiver concept with an additional integration of a spot size converter and a redesigned amplifier circuit was developed with these considerations in mind. This new generation of pinTWA Rx-OEICs comprise waveguide-integrated photodiodes with monolithically integrated taper and travelling wave amplifiers with a negative bias-configuration, avoiding an external bias network, and enables the cost effective packaging in a single-chip photoreceiver module with 47 GHz bandwidth.

40-Gbit/s photoreceiver modules for 1.55-/spl mu/m TDM system applications covering RZ and NRZ coding are described. The modules contain an InP-OEIC with a monolithic integration of a waveguide-integrated photodiode and a traveling-wave amplifier.

An InP-based monolithic integrated photoreceiver with a bandwidth of 27 GHz is presented. The device consists of a waveguide fed pin-photodiode and a traveling wave amplifier with coplanar waveguides based on four InAlAs/InGaAs/InP-HFET. The integration concept, receiver design, fabrication process and characterization are shown. The presented concept offers a potential for bit rates in the 100 Gb/s range.

Optical front-ends are considered to play a major role in future communication systems operating at bit rates of 20 or even 40 Gbit/s, as well as in mobile communication systems with fibre-optic distribution networks. Consequently, different approaches for the monolithic integration of high-speed receivers for a wavelength of 1.55 /spl mu/m can be found in the literature. In this paper, we report on the first monolithical integration of an optical receiver OEIC, which combines the advantageous high-speed characteristics of the waveguide integrated pin photodiode and of the travelling wave amplifier (TWA) circuit, both based on the InP material system.

For optical networks in the 40 Gbit/s regime as well as in fiber-fed cellular microwave mobile communication systems high-speed optical receivers with high sensitivity are required. This work describes the development of GaInAs-AlInAs high-electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on metal-organic vapour phase epitaxy (MOVPE) layers. These devices are to be used in low-noise amplifier circuits as part of an optical receiver.

The surface Fermi level of Ga/sub 0.47/In/sub 0.53/As and Al/sub 0.48/In/sub 0.52/As is determined by Hall measurements on InP-based HEMT-type van der Pauw structures without and with downstream PECVD SiN/sub x/ surface passivation. The passivation increases the surface Fermi level towards the conduction band-edge for both semiconductors in particular for low deposition temperatures. While the increase is clearly noticeable on GaInAs it appears less marked on AlInAs. From the finding that the resulting enhancement of carrier density in the GaInAs cap layer does not lower the DC channel resistivity of SiN/sub x/ passivated HEMT devices conclusions can be drawn about the path of the current in the source and drain regions.

Polarization diversity heterodyne receiver PICs including a tunable 4-section DBR laser as a local oscillator have been successfully fabricated for the first time. PIC design and fabrication are described and characteristics of the integrated laser components are presented.

An InP-based photoreceiver OEIC for /spl ges/40 Gbit/s data rate applications is presented. Besides a waveguide-integrated photodiode it contains a 38 GHz gain flattened distributed amplifier, which is composed of four HEMTs, fabricated by e-beam lithography.

InP-based PIN TWA photoreceiver OEICs with monolithically integrated taper were fabricated, pack-aged into butt-coupled pig-tailed modules and characterized for 50 GHz operation at /spl lambda/=1.55 /spl mu/m. Cascode-type circuit schemes of the integrated travelling wave amplifier were realized for increased conversion gain of up to 85 V/W.

A combination of an InP-based monolithically integrated photoreceiver with a spot size converter is presented. A total receiver conversion gain of more than 1A/W, an extended bandwidth of 47 GHz for error corrected 40 Gbit/s application are achieved.

Advanced 40 Gb/s photoreceiver OEICs, packaged into thermo-stable modules, were developed for 1.55 micron TDM applications. The OEIC comprises a waveguide-integrated photodiode and a traveling wave amplifier with a group delay scatter |/spl plusmn/7 ps| up to 45 GHz.

We report on the fabrication and characterization of a monolithically integrated balanced mixer receiver on InP consisting of a 3-dB coupler, twin balanced waveguide integrated photodiodes, and a low-noise electrical preamplifier. The receiver OEIC exhibits a transimpedance of 223 Omega and a 3-dB bandwidth of 1 GHz. Heterodyne operation and local laser noise cancellation capability of the OEIC are demonstrated. >

Structural and optical properties of thin InGaAsN insertions in GaAs, grown by molecular beam epitaxy using an RF nitrogen plasma source, have been investigated. Nitrogen incorporation into InGaAs results in a remarkable broadening of the luminescence spectrum as compared with that of InGaAs layer with the same indium content. Correspondingly, a pronounced corrugation of the upper interface and the formation of well defined nanodomains are revealed in cross-sectional and plan-view transmission electron microscope (TEM) images, respectively. Raising the indium concentration in InGaAsN (N

A detector stage comprising a photodiode, a field‐effect transistor, and a load resistor, and a wavelength demultiplexer have been monolithically integrated in the GaInAsP/InP material system. Chips were mounted into complete modules and operated in a 1.3 μm/1.55 μm bidirectional transmission link. At 576 Mbit/s and 10−9 bit error rate the sensitivity of the module was −21 dBm, while the intrinsic sensitivity of the receiver was determined to be −28 dBm.

Presently photonic-based telecommunication systems are upgraded to 40Gb/s single-channel data rates, while exploiting additional transmission capacity enhancement by WDM [1].

The molecular beam epitaxial growth of Si delta -doped donor planes within InGaAs layers is described. The results of Hall and C-V characterization measurements of single and double delta -doped InGaAs channel layers are presented. It is shown that high sheet carrier concentrations approaching 3.8*10/sup 13/ cm/sup -2/ can be achieved. Improved carrier transport in double delta -doped channels for FET applications is proposed and experimentally confirmed by decreased sheet resistance values obtained from double delta -doped structures. >

For future long-haul communication systems operating at bitrates of 40 Gbit/s and for broad-band mobile access systems using 38- or 60-GHz carrier frequencies, ultrafast photoreceivers have to be provided. Therefore, an integration concept for InP-based optoelectronic microwave monolithic integrated circuits for the 1.55-/spl mu/m wavelength regime is demonstrated, which allows independent optimization of the constituting devices. Two different types of photodetectors (PDs), a waveguide-integrated PIN photodiode (PD) and a top-illuminated metal-semiconductor-metal PD, both having bandwidths of up to 70 GHz, have been developed. These are fabricated together with different amplifier designs employing high electron mobility transistors which exhibit transit frequencies of up to 90 GHz. The application to a 40-Gbit/s broadband photoreceiver for high-bit-rate time-division multiplexing systems is reported, as well as the application to 38- and 60-GHz narrow-band photoreceivers for use as optic/millimeterwave converters in mobile communication systems.

We report on the successful monolithic integration of an InP-based photoreceiver operating in the narrow band around 38 GHz at a wavelength of 1.55 /spl mu/m, The optoelectronic integrated circuit (OEIC) incorporates two types of high-speed devices, a submicrometer metal-semiconductor-metal photodetector (MSM PD) made of InGaAs-InP and quarter-micrometer high-electron-mobility-transistors (HEMTs) based on a lattice-matched InGaAs-InAlAs-InP layer stack. For this purpose a fabrication process requiring only twelve main steps including a metal-organic chemical vapor deposition growth for the MSM PD layers and a MBE regrowth for the HEMT layers has been developed. At 38 GHz, a responsivity of 3.5 A/W for the OEIC is achieved.

A monolithic integrated photoreceiver for 1.55-/spl mu/m wavelength has been designed for operation in a 20-Gb/s synchronous digital hierarchy system (SDH/SONET), based on a new integration concept. The optoelectronic integrated circuit (OEIC) receiver combines a waveguide-integrated PIN-photodiode and a traveling wave amplifier in coplanar waveguide layout with four InAlAs/InGaAs/InP-HFETs (0.7-/spl mu/m gate length). The receiver demonstrates a bandwidth of 27 GHz with a low frequency transimpedance of 40 dB/spl Omega/. This is, to our knowledge, the highest bandwidth ever reported for a monolithic integrated photoreceiver on InP. Furthermore, a receiver sensitivity of -12 dBm in the fiber (20 Gb/s, BER=10/sup -9/) and an overall optical input dynamic range of 27 dB is achieved. Optical time domain multiplex (TDM) system experiments of the receiver packaged in a module show an excellently shaped eye pattern for 20 Gb/s and an overall sensitivity of -30.5 dBm (BER=10/sup -9/) [including erbium doped fiber amplifiers (EDFA)].

We report on the fabrication and characterization of AlInAs/GaInAs/InP high-electron mobility transistors (HEMTs) regrown by MBE on optical waveguide layers. A travelling wave amplifier (TWA), consisting of four HEMTs, is monolithically integrated with a pin photodiode and an optical waveguide to build a high-bit rate optical receiver on semi-insulating InP substrate. The 0.7 ?m gate HEMTs showed fT and fmax of 37 GHz and 105 GHz, respectively, which are well comparable to the performances of the reference devices grown on InP:Fe substrate. The devices are designed to exhibit their maxima of Gm, fT and fmax at Vgs=0V.

For the first time a packaged polarization diversity coherent receiver OEIC including detector units (photodetectors, JFET, load resistor) has been fabricated with the following data: waveguide loss 2 dB, 3 dB balance within 0.4 dB, polarization extinction >30 dB (TM) and >17 dB (TE), 3 dB cutoff frequency of 0.9 GHz, common mode rejection ratio 30 dB. >

The critical issues for the optimization of the MBE grown layer sequence for the integration of an optical waveguide, a PIN photodiode and a junction field effect transistor (JFET) to form a monolithical integrated receiver chip are discussed. For the JFET layer sequence low residual carrier density of the thick buffer layer has been successfully achieved. The growth of a p+/p++ gate contact layer with minimized acceptor diffusion behaviour is described. For the hybridly grown MOVPE(LPE) GaInAsP/MBE GaInAs PIN/waveguide structure optimum crystallinity is achieved; however, donor accumulation at the interface is detected. MBE grown AlGaInAs as an alternative for the waveguide layer has been investigated. Due to its high resistivity at growth temperatures below 500°C device isolation can be achieved.

The worldwide installation of broadband optical communication networks calls for high-performance opto-electronic integrated circuits (OEICs). In particular, balanced coherent heterodyne receiver OEICs are currently of great interest due to increased device functionality.1,2 The main advantage of such receivers compared to single-detector circuits is their near quantum noise limited performance in the presence of weak signals and intensity noise from the local oscillator.1 In this paper the successful fabrication of a monolithicaliy integrated receiver in the InGaAsP/InP material system, incorporating two semi-insulating ribwaveguides, balanced twin-photodiodes, a junction field effect transistor (JFET), and a resistor, is reported for the first time (Fig. 1). Such components may serve as important building blocks in the OEICs described above. The major advantages of our structure are as follows: 1) Ease of epitaxy: Possibility to grow all layers in one epitaxy on planar substrates. 2) Ease of electrical isolation between the two photodiodes as well as the JFET using semi-insulating InGaAsP for the waveguide layer,3 avoiding additional isolation techniques (e.g. etching, implantation, diffusion) or two-side wafer processing (as proposed in /4/).

The growth of extremely highly Be-doped (10/sup 19/-10/sup 20/ cm/sup -3/) InGaAs contact layers for JFET devices by molecular beam epitaxy was optimized with respect to minimizing the Be diffusion. Be diffusion coefficients were found to depend exponentially on Be concentration and strongly on the growth temperature. Hole concentrations and specific resistances of Ti-Au contacts were not influenced by the growth temperature in the investigated range of 350-500 degrees C. Fairly abrupt Be doping profiles in InGaAs were attained at growth temperatures of as low as 350 degrees C even at doping densities in the 10/sup 19/ cm/sup -3/ range. JFETs employing such an optimized layer structure exhibited very high transit frequencies of nearly 30 GHz (1- mu m gate length). >

Acceptor doping of MBE grown Ga0.47In0.53As on InP:Fe substrates utilizing manganese is investigated as an alternative for overcoming problems related to beryllium doping. The incorporation behaviour of manganese is analyzed in detail with respect to its application in optoelectronic device structures. Special emphasis is put on low-level and maximum-level doping relevant for use in buffer and contact layers, respectively. The dependence of activation energy and the degree of ionization on acceptor concentration is determined. At high doping levels the free-hole concentration is markedly lower than the doping concentration. It is attributed to the diffusion of acceptor species across the heterointerface into the substrate. Manganese diffusion is demonstrated to be an important effect for the interpretation of the measurement results. Manganese doping is applied in p+/n/p−-layer structures for junction field effect transistor applications. The intended abruptness of acceptor profiles is deteriorated by diffusion of manganese in the Ga0.47In0.53As material. The degraded device characteristics obtained are attributed to the acceptor diffusion behaviour established.

Polarisation diversity heterodyne receiver OEICs including a tunable four-section DBR laser as a focal oscillator have been successfully fabricated for the first time. OEIC design and fabrication are described and first characteristics of the integrated subcomponents and a packaged receiver OEIC are presented.

A monolithically integrated photoreceiver is presented, based on a new integration concept comprising a waveguide integrated photodiode and a travelling wave GaInAs/AlInAs-HEMT amplifier. A record 3 dB bandwidth of 27 GHz is measured and a clearly open eye is obtained for a 20 Gbit/s pseudo-random bit stream. This high speed performance was achieved with photolithographically defined 0.7 µm gate length HEMTs, regrown by MBE on semi-insulating GaInAsP waveguide layers.

For the first time a monolithically integrated InP-based photoreceiver (OEIC) for narrow band applications in the 38 GHz range is reported. It consists of a top-illuminated submicron MSM photodetector and a three stage coplanar HEMT amplifier.

We report on our recent results on the monolithic integration of InP-based narrow band photoreceiver OEICs for 1.55 /spl mu/m working in the 60 GHz range. These OEICs were achieved by successive improvement of the design and fabrication techniques used for OEICs working in the 38 GHz regime. The OEICs combine two types of high-speed devices, a top-illuminated InGaAs-InP metal-semiconductor-metal photodetector (MSM PD) with 0.2 /spl mu/m feature and 0.15 /spl mu/m high-electron-mobility-transistors (HEMT) based on InGaAs-InAlAs-InP.