Richard Matz

Facet growth in selective area epitaxy of Inp by MOMBE

Abstract InP facet growth near SiO 2 mask edges during metalorganic molecular beam epitaxy is studied for various V/III ratios on (100) substrates with 2° misorientation towards (110). While ideal vertical layer growth occurs at high V/III ratio even up to 2 μm growth thickness, oblique (111) planes are kinetically favoured near mask edges at lower V/III ratio. The V/III ratio is a key parameter since it determines the facets with the lowest kinetically limited growth rate at the border of the growing layer. Also the diffusion length of mobile adsorbed species, by which additional features near mask edges and corners are explained, decreases with V/III ratio. Besides interfacet diffusion driven by concentration gradients between facets of different growth rate, there is evidence also for anisotropic diffusion along [0–1] on (100) InP. We speculate that this is the origin of the fine surface ripples on InP surfaces observed on one side near the SiO 2 masks.

Wide piezoelectric tuning of ltcc bandpass filters

The increasing number of frequency bands and services in wireless communications is causing a demand for analogue active and passive frontend components with wide bandwidth or tuning range, respectively. Similar to micro-electromechanical systems (MEMS), this work presents a parallel plate capacitor with multilayer dielectrics and piezoelectrically movable top electrode as an advantageous tunable element with no addition of any lossy material. When applied as a shunt capacitor in a coupled microstrip-line LTCC bandpass filter, the center frequency of the filter is tuned from 1.1 GHz to 2.6 GHz with 200 V control voltage and low insertion loss of 2 to 4 dB. The analysis of the device by full-wave simulation reveals a potential tuning range from 0.8 GHz to 2.8 GHz when the thin-film processability of the LTCC surface is properly controlled.

Development of a photonic integrated transceiver chip for WDM transmission

With the observed expansion of fiber-optic networks and the movement of line terminals towards the individual customer the need for cost-effective fabrication of customer access modules for interactive services arises. Monolithic integration of the module functions on InP is frequently seen as a means to reduce module costs. Here we describe a generic fabrication process for InP photonic integrated circuits and demonstrate an initial transceiver chip with transmit, receive and 1300/1530 nm wavelength division multiplexing functions. The chip output power reaches 1 mW at 1530 nm with a laser threshold current of 20 mA. The detection efficiency at 1300 nm is 0.1 A/W of fiber power.<<ETX>>

0.8 GHz to 2.4 GHz Tunable Ceramic Microwave Bandpass Filters

A 200% tuning range of advanced integrated piezoelectric LTCC bandpass filters is presented. The filter incorporates a novel parallel-plate capacitor that can be tuned by a piezoelectrically movable electrode. In this prototype, the fabrication process is modified for better controlling the air-gap inside the capacitor. To our knowledge, the potential recorded tuning range from 0.8 GHz to 2.4 GHz is the highest continuous range that ever reported in bandpass filters.

Photonic integrated transceiver for the access network

To reduce fabrication costs of fibre-optic terminal modules for interactive services, an InGaAsP/InP chip fabrication process has been developed for monolithic integration of a strained-layer multiple quantum well laser, a monitor diode and a photoreceiver with a 1300/1530nm filter. Reception responsivity and output power of the chips are 0.1 AW-1 at 1300nm wavelength and 4.5mW at 1530nm wavelength, respectively. At present, complete modules with fibre pigtail exhibit 0.7mW launch power, but 1.4 mW is expected with the latest chips.

Selective-area growth of III/V semiconductors in chemical beam epitaxy

This review describes progress in selective-area epitaxy (SAE) using masked wafers in chemical beam epitaxy (CBE). Surface-selective growth is discussed, leading to a better understanding of the growth phenomena taking place in the transition areas from growth to non-growth where crystal facets are formed. On the basis of this knowledge it is demonstrated that unique structures with uniform layer thickness and material compositions can be obtained, which are not dependent on the aspect ratio of the masked area. This enables the device designer to produce a flexible mask layout which is not limited by the growth mechanism. Finally the authors current knowledge about SAE of device structures grown by CBE MOMBE is reviewed.

Phase-Shifted Holographic Gratings For Distributed Feedback Lasers

The generation of phase-shifted gratings in InP for DFB lasers by holographic double exposure is described. The method is also suited for maskless laser activated etching. An estimation of the DFB laser threshold as compared to the ideal phase-shifted grating with constant amplitude is given.

Novel III/V heterostructures fabricated by metalorganic molecular beam epitaxy

More sophisticated III-V devices and the challenge of integration require material growth over structured surfaces. Of particular interest are the Ga-In-As-P materials. Due to the surface selective growth in metalorganic molecular beam epitaxy a high degree of perfection in locally grown structures can be achieved. However, a clear picture of the growth mechanism on various crystal planes and structures helps optimizing the so-called selective area epitaxy. These mechanisms, in respect to relevant epitaxial parameters (V-III-ratio, rate, crystal orientation) with emphasis on lateral butt coupling structures into various crystal directions is discussed. Application of in situ grown lateral heterojunctions for e.g. laser-amplifier wave-guide integration are presented.

Laser wet etching of diffraction gratings in GaAs for integrated optics

A6stract-Submicrometer optical gratings with high-aspect ratios were produced in (lOO)-n-GaAs by a two-step wet-etching process using maskless holographic laser etching to launch initial grating growth and subsequent anisotropic dark etching to amplify the microstructure imprinted by the laser. Time-dependent etch rates and nonsinusoidal groove profiles during the initial stage are described by a minority carrier diffusion model.

Power Inductors in Ceramic Multilayer Circuit Boards

Power electronic inductors, with values of several μH, have been integrated into thermally stable ceramic multilayer circuit boards by the use of NiZnCu and MnZn ferrite tapes in low temperature cofired ceramic (LTCC) technology. These ferrites are particularly attractive for switched mode power supplies in automation, drives, and consumer applications, where the miniaturization of modules is triggered by advances in transistor technology and switching frequencies. The small signal analysis of embedded individual inductors and coupled transformer coils reveals the generic design rules for these components and additional materials properties beyond those accessible by ring core measurements. In the process of adapting the materials to LTCC, the distinct differences between the two materials become blurred, for example, they can be engineered to exhibit similar cutoff frequencies. NiZnCu ferrite, which is sinterable in air, may even achieve higher permeability than MnZn ferrite. The latter, however, shows h...