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Your search keyword '"Bolognesi, C. R."' showing total 217 results
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217 results on '"Bolognesi, C. R."'

18. Growth and characterization of iron-doped semi-insulating InP buffer layers for Al-free GaInP/GaInAs high electron mobility transistors.

Author

Ostinelli, O., Alt, A. R., Lövblom, R., and Bolognesi, C. R.

Subjects
INDIUM phosphide, GALLIUM compounds, TRANSISTORS, GALLIUM arsenide, ELECTRON mobility
Abstract

We characterize the resistivity of InP buffer layers deposited by metal-organic vapor-phase epitaxy for the fabrication of Al-free GaInP/GaInAs high electron mobility transistors (HEMTs). Achieving highly-resistive InP buffer layers on semi-insulating (SI) InP:Fe substrates has long been recognized to be challenging. This is particularly true in HEMT applications because such devices are especially sensitive to the deleterious effects of buffer leakage currents. Our experiments show that impurities arising from the SI InP substrate as well as from reactor parts produce an overall n-type doping concentration of n=1-10×1016 cm-3 near the buffer/substrate interface, which decays exponentially to a level of 4×1014 cm-3 after approximately 1 μm of InP growth. This nonintentional impurity incorporation leads to a parasitic channel in the buffer and a current leakage path for the HEMT structures, regardless of the growth conditions used. Highly-insulating buffer layers could however be obtained with InP doped by Fe at a concentration of 6×1016 cm-3 in a thin region near the InP:Fe substrate. The sheet resistance consequently increased from RS=3 000 Ω/□ for the not intentionally doped InP layers to RS=9.4×107 Ω/□ when Fe-doping is used in the buffer layers, a value suitable for the realization of high-speed HEMTs. As a demonstration vehicle, Al-free pseudomorphic T-gate GaInP/GaInAs HEMTs with a 100 nm footprint were fabricated and achieved a cutoff frequency of fT=fMAX∼250 GHz based on a still nonoptimized channel structure featuring a mobility and sheet carrier concentration of 10 000 cm2/V s and 1012 cm-2, respectively. The present work differentiates itself from previous Fe doping studies of InP by clarifying and quantifying the physical processes leading to parasitic conduction in not intentionally doped InP buffer layers grown on InP:Fe substrates. [ABSTRACT FROM AUTHOR]

Published
2010
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19. Kirk effect mechanism in type-II InP/GaAsSb double heterojunction bipolar transistors.

Author

Tao, N. G. and Bolognesi, C. R.

Subjects
*BIPOLAR transistors, *QUANTUM tunneling, *HETEROJUNCTIONS, *GALLIUM compounds, *ELECTROSTATIC accelerators
Abstract

The Kirk effect mechanism is studied in type-II InP/GaAsSb/InP NpN double heterojunction bipolar transistors (DHBTs) both experimentally and through two-dimensional hydrodynamic numerical simulations. We show that the large valence band discontinuity ΔEV at the GaAsSb–InP base/collector heterojunction does not allow hole injection into the InP collector as is the case in homojunction collectors. Instead, a blocking barrier is electrostatically induced in the base layer at high collector current densities: this barrier increases base recombination and decreases the current gain. We show that tunneling transport must be considered at the base/collector heterojunction and that the induced barrier depends on the base layer doping level—effectively, InP/GaAsSb DHBTs display high-current limitations that are also controlled to some extent by the base doping level. [ABSTRACT FROM AUTHOR]

Published
2007
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22. Raman scattering study of InAs/GaInSb strained layer superlattices.

Author

Sela, I., Campbell, I. H., Laurich, B. K., Smith, D. L., Samoska, L. A., Bolognesi, C. R., Gossard, A. C., and Kroemer, H.

Subjects
RAMAN effect, SUPERLATTICES, MOLECULAR beam epitaxy, BACKSCATTERING
Abstract

Presents a Raman scattering study of strained layer superlattices. Application of molecular beam epitaxy in the growth of the superlattices; Determination of structural parameters by Rutherford backscattering and x-ray diffraction; Experimental details; Result of the study.

Published
1991
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23. Accuracy of Microwave Transistor fT and fMAX Extractions

Author

Teppati Valeria, Tirelli Stefano, Lövblom Richard, Flückiger Ralf, Alexandrova Maria, and Bolognesi C. R.

Subjects
millimeter wave device, Integrated circuit measurements, Evaluation of Measurement Uncertainty, millimeter wave technology, millimeter wave transistors
Abstract

We present a complete methodology to evaluate the accuracy of microwave transistor figures of merit f T (cur rent gain cut off frequency) and f MAX (maximum oscillation frequency). These figures of merit are usually extracted from calibrated S parameter measurements affected by residual cali bration and measurement uncertainties. Thus the uncertainties associated with f T and f MAX can be evaluated only after an accurate computation of the S parameters uncertainties. This was done with the aid of two recently released software tools. In the uncertainty propagation the standard de embedding techniques are assumed to be error free but still contributing to the final uncertainty budget with their measurement uncertainty. We also present an analysis on how different interpolation/extrapolation methodologies affect uncertainty. In addition an overview of the possible causes of errors and suggestions on how to avoid them are given. With the continued rise of reported f T /f MAX values this study has become necessary in order to evaluate the accuracy of these these figures of merit both by adding confidence intervals to their values and by identifying possible extraction errors.

Published
2014

25. Quaternary Graded-Base InP/GaInAsSb DHBTs With ${f}_{\text{T}}$ / ${f}_{\text{MAX}}$ = 547/784 GHz.

Author

Quan, Wei, Arabhavi, Akshay M., Fluckiger, Ralf, Ostinelli, Olivier, and Bolognesi, C. R.

Subjects
HETEROJUNCTION bipolar transistors, METAL organic chemical vapor deposition, INDIUM phosphide
Abstract

We report a “Type-II” metal–organic chemical vapor deposition (MOCVD)-grown compositionally graded quaternary base InP/GaInAsSb/InP double heterojunction bipolar transistor (DHBT) with simultaneous cutoff frequencies ${f}_{\text {T}}/{f} _{\text {MAX}}$ = 547/784 GHz. Compositional grading of the As/In mole fractions enables stronger quasi-electric fields in the base and favors better RF performance. Consideration of the higher bandstructure reveals new insights on the performance limits of “Type-II” DHBTs: Indium incorporation in a GaAsSb base appears to increase the efficiency of electron injection from the base into the InP collector. The present results correspond to the fastest MOCVD-grown quaternary base DHBTs reported to date for a device with ${f} _{\text {MAX}}>{f}_{\text {T}}$. [ABSTRACT FROM AUTHOR]

Published
2018
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49. High‐speed and low‐noise AlInN/GaN HEMTs on SiC

Author

Sun, Haifeng, primary, Alt, Andreas R., additional, Benedickter, Hansruedi, additional, Feltin, Eric, additional, Carlin, Jean‐François, additional, Gonschorek, Marcus, additional, Grandjean, Nicolas, additional, and Bolognesi, C. R., additional

Published
2010
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