Characteristics of coplanar transmission lines on multilayer substrates expressed in analytic formulas have been obtained using conformal mapping. The accuracy of these formulas has been verified experimentally on a variety of coplanar transmission lines using differential electro-optic (DEOS) sampling. For coplanar waveguides, the theory differs from the experiment by less than 3%; for coplanar striplines, the differences are less than 6%.

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Characteristics of coplanar transmission lines on multilayer substrates: modeling and experiments

III-V semiconductors, GaAs and in particular InGaP, are used in many different electronic applications, such as high power and high frequency devices, laser diodes and high brightness LED. Their direct bandgap and high reliability make them ideal candidates for the realisation of high efficiency solar cells: in the past years they have been successfully used as power sources for satellites in space, where they are able to produce electricity from sunlight with an overall efficiency of around 30%. Nowadays, the use of arsenides and phosphides as photovoltaic (PV) devices is confined only to space applications since their price is much higher than conventional Si flat panel modules, the leading PV market technology. But with the introduction of multijunction solar cells capable of operating in high concentration solar light, the area and, therefore, the cost of these cells can be reduced and will eventually find an application and market also on Earth. This article will review the situation of semiconductor solar cell materials, focusing on Si, GaAs, InGaP and multijunction solar cells and will discuss future trends and possibilities of bringing III-V technology from space to Earth. Copyright © 2006 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pip.715

The potential of III-V semiconductors as terrestrial photovoltaic devices

Issues important for the manufacturing of GaAlAs/GaAs heterojunction bipolar transistors (HBTs) and their prospects for application in various areas are discussed. The microwave and digital performance status of HBTs is reviewed. Extrapolated values of maximum frequency of oscillation above 200 GHz and frequency divider operation at 26.9 GHz are reported. Key prospects for further device development are highlighted. >

GaAlAs/GaAs heterojunction bipolar transistors. Issues and prospects for application

Next-generation high data rate wireless communication systems offer completely new ways to access information and services. To provide higher data speed and data bandwidth, RF transceivers in next-generation communications are expected to offer higher RF performance in both transmitting and receiving circuitry to meet quality of service. The semiconductor device technologies chosen will depend greatly on the tradeoffs between manufacturing cost and circuit performance requirements, as well as on variations in system architecture. It is hard to find a single semiconductor device technology that offers a total solution to RF transceiver building blocks in terms of system-on-chip integration. The choices of device technologies for each constituent component are important and complicated issues. We review the general performance requirement of key components for RF transceivers for next-generation wireless communications. State-of-the-art high-speed transistor technologies are presented to assess the capabilities and limitations of each technology in the arena of high data rate wireless communications. The pros and cons of each technology are presented and the feasible semiconductor device technologies for next-generation RF transceivers can be chosen upon the discretion of system integrators.

Device technologies for RF front-end circuits in next-generation wireless communications

Recent results from a Swedish program for development of 60-GHz monolithic microwave integrated circuits (MMICs) for high-data-rate communication links are presented. Front-end circuits such as mixers, amplifiers, frequency multipliers, IF amplifiers with gain control, and voltage-controlled oscillators (VCOs) have been realized utilizing GaAs PHEMT and MHEMT technologies. A newly developed 7.5-GHz coupled Colpitt VCO shows a minimum phase noise of -95 dBc at 100 kHz offset. A second-harmonic 14-GHz VCO shows a minimum phase noise of less than -90 dBc at 100 kHz. A novel balanced 7-28-GHz MMIC frequency quadrupler is described and compared with a single-ended quadrupler at the same input frequencies. To demonstrate its feasibility and potential application, the quadrupler is combined with the Colpitt VCO and the output characteristics of the resulting 30-GHz MMIC source are measured. A three-stage MHEMT wide-band amplifier covering 43-64 GHz with a gain of 24 dB, a minimum noise figure of 2.5 dB, and a passband ripple of 2 dB is also described. In future 60-GHz systems for mass markets where cost is of utmost importance, Si-based technologies, especially CMOS, are highly interesting. Some recent circuit results based on a 90-nm CMOS technology are also reported.

Development of 60-GHz front-end circuits for a high-data-rate communication system

A self-aligned InGaP/GaAs heterojunction bipolar transistor with a compositionally graded In/sub x/Ga/sub 1-x/As base has been demonstrated with f/sub T/=83 GHz and f/sub max/=197 GHz. To our knowledge, these results are the highest reported for both parameters in InGaP/GaAs HBT's. The graded base, which improves electron transport through the base, results in a DC current gain and a cutoff frequency which are 100% and 20% higher, respectively, than that achieved by an identical device with a nongraded base. The high f/sub max/ results from a heavily doped base, self-aligned base contacts, and a self-aligned collector etch. These results demonstrate the applicability of InGaP/GaAs HBT's in high-speed microwave applications.

High-speed InGaP/GaAs HBTs with a strained In/sub x/Ga/sub 1-x/As base

We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3/spl times/10 /spl mu/m/sup 2/ emitter finger device achieved a cutoff frequency of f/sub T/=66 GHz and a maximum frequency of oscillation of f/sub max/=109 GHz. A minimum noise figure of 1.12 dB and an associated gain of 11 dB were measured at 4 GHz. These results are the highest combined f/sub T/+f/sub max/ and the lowest noise figure reported for an InGaP/GaAs HBT and are attributed to material quality and the use of self-aligned base contacts. These data clearly demonstrate the viability of InGaP/GaAs HBT's for high-speed, low-noise circuit applications.

High-speed, low-noise InGaP/GaAs heterojunction bipolar transistors

Ka-band voltage controlled oscillators (VCOs) have been designed using InGaP/GaAs HBT technology. The best measured VCO shows a phase noise of -95 dBc/Hz at 100 kHz offset and -112 dBc/Hz at 1 MHz offset, delivering 5.3 dBm output power at 40.8 GHz. Variations of circuit topology and resonator type were fabricated to evaluate their contribution to phase noise and tuning range.

Low phase noise Ka-band VCOs using InGaP/GaAs HBTs and coplanar waveguide

To improve electrical isolation and simplify the heterojunction bipolar transistor (HBT) fabrication process, a semi-insulating InGaP buffer layer has been employed in an InGaP/GaAs HBT. Data is presented that demonstrates this buffer layer serves as an excellent isolation material. In addition, high-frequency HBT's have been fabricated and characterized to show that the buffer layer does not degrade device performance.

InGaP/GaAs heterojunction bipolar transistor grown on a semi-insulating InGaP buffer layer

A novel HBT structure has been utilized to fabricate emitter ledges using a simple, selective wet chemical etch process. This structure eliminates the need for photoresist or dielectric etch masks in the fabrication of self-aligned ledges and enables the use of highly-selective wet chemical etches in forming an InGaP ledge. Small-area devices have been demonstrated with improved gain and excellent high-frequency performance.

M.T. Fresina

Papers

High-speed InGaP/GaAs HBTs with a strained In/sub x/Ga/sub 1-x/As base

High-speed, low-noise InGaP/GaAs heterojunction bipolar transistors

Low phase noise Ka-band VCOs using InGaP/GaAs HBTs and coplanar waveguide

InGaP/GaAs heterojunction bipolar transistor grown on a semi-insulating InGaP buffer layer

InGaP/GaAs HBT with novel layer structure for emitter ledge fabrication