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Papers by Claudio Lanzieri

The European Physical Journal B, 2000

ABSTRACT : GaAs Schottky diodes, made on semi-insulating liquid encapsulated Czochralski grown ma... more ABSTRACT : GaAs Schottky diodes, made on semi-insulating liquid encapsulated Czochralski grown material with concentrations of acceptor dopants varying from 1014 to 1017 cm-3, were investigated as alpha particle detectors. The charge collection efficiency (CCE) was found to decrease dramatically with increasing . Optical spectra in transmittance and reflectance were accurately measured to determine the concentrations of both neutral and ionised EL2 defects as a function of . The concentration of ionised EL2+ centres was shown to increase with , and to be quasi inversely proportional to the CCE values. This behaviour strongly supports the hypothesis that the EL2 defects play the main role in the compensation of the material and in limitation of the detection properties.

In this article we illustrate how the noise performance of ion-implanted MESFET devices can be ap... more In this article we illustrate how the noise performance of ion-implanted MESFET devices can be appreciably improved by means of optimised pre and post implant annealing cycle. With this technique the 12 GHz noise figure of 0.5x300 um devices is reduced from 2.7 dB to 1.8 dB.

In this paper a first iteration X-band T/R module based on a GaN-HEMTMMICFront-End chip-set, comp... more In this paper a first iteration X-band T/R module based on a GaN-HEMTMMICFront-End chip-set, comprising a power amplifier, robust low-noise amplifier andpower switch will be presented. Even though ultimate T/R moduleperformance cannot be achieved with current GaN-HEMTtechnological maturity the impact that this technology can have at systems level in terms ofperformance/cost trade-off will be illus trated by means ofa preliminary innovative module archi tecture which foresees the elimination of more traditional T7R module components such as ferrite circulator and lim iterforfront-end signal routing andprotection.

Nuclear Physics B - Proceedings Supplements, 1999

MRS Proceedings, 1995

Ohmic contact has been observed to play an important role in the performances ofLiquid Encapsulat... more Ohmic contact has been observed to play an important role in the performances ofLiquid Encapsulated Czochralski gallium arsenide particle detectors since it is possible to control the injection of charge carriers which determines the device performances. Alloyed and implanted contacts characteristics have been compared to relate the presence of electrically active defects induced during contact preparation to the final detector efficiency. In-situ optical probing investigations have been carried out to analyze the electric field distribution. Spectroscopic investigations show that the contact fabrication process significantly influences the trap density, whilst it does not change their type.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1995

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994

Progress in Crystal Growth and Characterization, 1989

Reverse-bias testing in AlGaN/GaN HEMTs at high (negative) gate voltage is found to induce a cata... more Reverse-bias testing in AlGaN/GaN HEMTs at high (negative) gate voltage is found to induce a catastrophic increase in gate leakage current IG, with only a slight degradation of drain current ID. Electroluminescence (EL) microscopy demonstrates that leakage current injection is localized within "hot spots" at the gate edges, possibly corresponding to defects in the semiconductor material or at the metal-semiconductor interface. The density of "hot spots" increases during tests and is correlated with the increase of IG and electroluminescence intensity and with an enhancement of trapping effects such as current collapse. Index Terms—Current collapse, electroluminescence (EL), fail- ure mechanism, GaN, high-electron-mobility transistor (HEMT), reverse-bias.

This paper presents the results obtained both by experimental measurements and numerical simulati... more This paper presents the results obtained both by experimental measurements and numerical simulations carried out on state-of-the-art field plated GaAs-based pHEMTs.The effect of the field-plate length on DC and RF operation will be discussed showing that the adoption of an optimal field-plate structure can significantly boost the device RF power performance, resulting in power density up to 2W/mm measured at 2 GHz

Infrared Physics & Technology, 2008

An active two dimensional near field imaging of a High Electron Mobility Transistor (HEMT) used a... more An active two dimensional near field imaging of a High Electron Mobility Transistor (HEMT) used as THz detector has been performed. The reflective imaging system developed at the ENEA FEL Facility in Frascati has been used to this purpose. This imaging technique has shown to be particularly powerful in resolving various coupling mechanisms of the incident radiation with the device.

IEEE Transactions on Electron Devices, 2006

In this article we will report on a high yield HEMT/PM-HEMT technology, based an optimised ohmic ... more In this article we will report on a high yield HEMT/PM-HEMT technology, based an optimised ohmic contact formation and gate recessing. With this technology active device fabrication yields are better than 90% and corresponding key parameter tollerances always better than ± 5%, as required for high yield MMIC fabrication.

In this article we describe a global design approach of an X-band Tx/Rx module which, by means of... more In this article we describe a global design approach of an X-band Tx/Rx module which, by means of a Multi Chip Module (MCM) technique, includes in a single package the different microwave functions (4-bit phase-shifter, low-noise amplifier, power amplifier, switching control circuits), the thin film interconnections, the bias circuits, the driver circuits (Si ICs) and the switching MOS.

This work investigates, through the use of numerical drift-diffusion simulations, the hot electro... more This work investigates, through the use of numerical drift-diffusion simulations, the hot electron degradation mechanisms of power AlGaAs/GaAs HFETs. The experimentally observed degradation modes can be consistently explained by a negative charge storage at the device surface over the gate-drain access region.

An extensive power characterization of devices fabricated on GaN grown on SiC and sapphire substr... more An extensive power characterization of devices fabricated on GaN grown on SiC and sapphire substrates has been carried out, including powers weep and load-pull measurements in different bias conditions from class A to class B. An active load-pull bench optimized for high voltage and high power measurements allows to extend the load-pull characterization to the whole Smith chart, and to localize the optimum load conditions even for devices with almost reactive optimum terminations. The characterization procedure allows to verify scaling rules and the effects of defects and thermal degradation on the device power performances. The results of the SiC and sapphire-based devices show that, on one side, SiC-based devices exibit state-of-the-art performances in Class A, and, on the other side, low-cost sapphire-based devices, when biased in high efficiency classes, can be viable candidates for medium power applications, despite the higher thermal resistivity of sapphire compared with the o...

This paper presents a new technology for the realization of multifunction self-aligned-gate GaAs ... more This paper presents a new technology for the realization of multifunction self-aligned-gate GaAs MESFET's (SAGFET) through multiple implantation of silicon and carbon. The carbon different behaviour as shallow or deep acceptor as a function of annealing parameters and fluorine co-implantation is discussed and evidence is given that, being a carbon buried layer effective for carrier confinement in the active channnel, DC and RF performances can be considerably improved with respect to ordinary recess-gate MESFET's both for power and low-noise devices.

1999 IEEE International Reliability Physics Symposium Proceedings. 37th Annual (Cat. No.99CH36296)

ABSTRACT This work describes results of hydrogen degradation experiments performed on Al/Ti-gate ... more ABSTRACT This work describes results of hydrogen degradation experiments performed on Al/Ti-gate AlGaAs-GaAs power HFETs. Upon storage at 180°C for times up to a hundred hours in either 5% or 15% H2 -N2 mixtures, the HFETs undergo significant changes in their electrical characteristics due to mechanisms located either under the gate (bulk effects) or on the surface access regions on the gate sides (surface effects). The former lead to a threshold voltage reduction and thus to an increase in the drain current, attributed to TiH formation in the gate and the attendant piezoelectric charge in the underlying semiconductor; a degradation of the peak transconductance is also observed. As for the surface effects, we measure an increase of source-gate and drain-gate breakdown voltages, due to surface-state creation on the gate sides and to electron capture therein