A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.

Wireless sub-THz communication system with high data rate

Infrared (2–12 μm) solid-state laser sources: a review

The wavelength range around 2 μm which is covered by the laser systems described in this chapter is part of the so called “eye safe” wavelength region which begins at about 1.4 μm. Laser systems that operate in this region offer exceptional advantages for free space applications compared to conventional systems that operate at shorter wavelengths. This gives them a great market potential for the use in LIDAR and gas sensing systems and for direct optical communication applications. The favourable absorption in water makes such lasers also very useful for medical applications. As it can be seen in figure 1, there is a strong absorption peak near 2 μm which reduces the penetration depth of this wavelength in tissue to a few hundred μm.

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2 µm Laser Sources and Their Possible Applications

This paper critically investigates the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation. The article is divided in two parts within Part I. 1) We analyze how the choice of the measurement and analysis parameters (such as the voltage levels used to induce the trapping phenomena and monitor the current transients, the duration of the filling pulses, and the method used for the extrapolation of the time constants of the capture/emission processes) can influence the results of the drain current transient investigation and can provide information on the location of the trap levels responsible for current collapse. 2) We present a database of defects described in more than 60 papers on GaN technology, which can be used to extract information on the nature and origin of the trap levels responsible for current collapse in AlGaN/GaN HEMTs. Within Part II, we investigate how self-heating can modify the results of drain current transient measurements on the basis of combined experimental activity and device simulation.

Deep-Level Characterization in GaN HEMTs-Part I: Advantages and Limitations of Drain Current Transient Measurements

We present an overview of solid-state integrated circuit amplifiers approaching terahertz frequencies based on the latest device technologies which have emerged in the past several years. Highlights include the best reported data from heterojunction bipolar transistor (HBT) circuits, high electron mobility transistor (HEMT) circuits, and metamorphic HEMT (mHEMT) amplifier circuits. We discuss packaging techniques for the various technologies in waveguide modules and describe the best reported noise figures measured in these technologies. A consequence of THz transistors, namely ultra-low-noise at cryogenic temperatures, will be explored and results presented. We also present a short review of power amplifier technologies for the THz regime. Finally, we discuss emerging materials for THz amplifiers into the next decade.

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An Overview of Solid-State Integrated Circuit Amplifiers in the Submillimeter-Wave and THz Regime

Tapered diode lasers in external resonator configuration are suitable for applications such as frequency conversion or non-linear spectroscopy were narrow linewidth in combination with high output power is needed. In order to increase the brightness it is necessary to make the output power and the efficiency comparable to broad area lasers and simultaneously keep the beam quality nearly diffraction limited. For this purpose we have grown low modal gain, single quantum well InGaAs/AlGaAs devices emitting at 980 nm by molecular beam epitaxy. As an example of a tapered laser with an overall length of 3.5 mm, we achieved an optical output power of more than 5 W in continuous wave mode (cw).

5 W high-efficiency high-brightness tapered diode lasers at 980 nm

Surface Passivation of InGaAs/InP HBTs Using Atomic Layer Deposited Al2O3

Wideband amplifiers for the next generation of T/R modules in future active array antennas are realized as monolithically integrated circuits (MMICs) on the basis of novel InAlGaN/GaN high electron mobility transistor (HEMT) structures. All designs are realized in microstrip transmission line technology. The wideband amplifier MMICs operate up to a frequency of 18GHz. A number of measurements have been performed, including small signal S-parameter and large signal power measurements. To our knowledge, these are the first MMICs based on InAlGaN/GaN HEMTs epitaxy for wideband applications in microstrip transmission line technology.

InAlGaN/GaN MMICs in microstrip transmission line technology for wideband applications

Highperformance integrated circuits and modulesformillimeter-wave applications basedon metamorphic InAIAs/lnGaAs HEMTson 4"GaAssubstrates arepresented. Anextrinsic transit frequency of410GHzfor 50nm gatelength devices isachieved. TheIC process features high yield on bothtransistor andcircuit levels. Two- stagelow-noise amplifiers demonstrate asmall signal gainof 20dBanda noise figure of2.4dBat94GHz.Anamplifier MMIC developed forG-bandoperation exhibits a gainof 21dB at220GHz.High-gain modulesfeaturing low-noise performance artediscussed whichenable novel applications, such asmillimeter-wave imaging up to220GHz. IndexTerms - FETs,FET amplifiers, low-noise amplifiers.

Advanced mm-WaveICsandApplications

Due to its outstanding materials properties the semiconductor system (Al,Ga)N is a very promising candidate for high power electronic applications covering communication, radar and power conversion. In fact GaN is already considered to be the most important semiconductor besides silicon. In this invited contribution we give an overview of epitaxial growth, device processing, characterization and reliability assessment of electronic devices based on this material.

Michael Mikulla

Papers

5 W high-efficiency high-brightness tapered diode lasers at 980 nm

Surface Passivation of InGaAs/InP HBTs Using Atomic Layer Deposited Al2O3

InAlGaN/GaN MMICs in microstrip transmission line technology for wideband applications

Advanced mm-WaveICsandApplications

Recent developments in GaN HEMTs and MMICs for high power electronics