Physics of semiconductors and advanced crystals

Physics of semiconductors and advanced crystals

Staff

Alberto Carnera, Andrea GasparottoEnrico NapolitaniDavide De Salvador, Andrea Sanson (Researcher), Marco Bazzan (Researcher), Sara Maria Carturan (degree technical staff), Gianluigi Maggioni (degree technical staff), Luca Bacci (technical staff).

PostDoc/Phd students

Ruggero Milazzo, Francesco Sgarbossa, Chiara Carraro.

Research Activity

The group of Semiconductors and Advanced Crystals has the aim of developing innovative processes for future semiconductor devices and advanced materials, exploiting the competences about chemical profiling, structural and electrical characterization, lattice vibrational dynamics, modelling, and out-equilibrium diffusion phenomena in solid state matter. The group make research at DFA with different lab instrumentations:
-    Secondary ion mass spectrometry (SIMS)
-    High resolution X-ray diffraction (HRXRD)
-    Van der Paw - Hall also at cryogenic temperatures
-    Rapid Thermal Processing
-    Laser Processing (upcoming)
-    Czochralski growth laboratory
-    Optics laboratory

At the close Laboratory Nazionali di Legnaro the group has access -in the framework of UNIPD-DFA/INFN-LNL collaboration agreement- to other facilities:
-    Rutherford Backscattering Spectrometry/ Nuclear Reaction Analysis with channeling equipment
-    Clean room and chemical lab
-    Sputtering systems

Moreover, the group periodically accesses to international Synchrotron Radiation facilities (ESRF, ELETTRA) for x-ray absorption fine structure (XAFS) experiments and to the Vibrational Spectroscopy laboratory of the University of Verona for Raman measurements. 


Main research lines


Nanoscale doping

(Enrico Napolitani, Davide De Salvador, Alberto Carnera)
Doping process has to be understood at nanoscale for successful design of future semiconductor devices. Basic experimental studies and modelling are being developed on silicon nanoclusters system.


Germanium doping

(Enrico Napolitani, Davide De Salvador, Alberto Carnera, Andrea Sanson)
Germanium is having a renewed interest for its application in nanelectronics and photonics (IR-detectors and lasers, plasmonics, photovoltaics,...). Research about doping processes has to be developed at various levels: experiments about standard processes (diffusion, ion implantation) has to be investigated and modelled to transfer the mature design ability on Si to Ge; moreover, innovative processes have to be investigated to dress growing performance request: very high doping, compatibility with nanoscale and high purity.
-    Laser annealing is one of the most promising technique for high level activation
-    Doping of high purity Ge is a particular task crucial for the developing of innovative gamma-ray detector systems
-    Molecular doping is a promising strategy for nanostructures doping.


Crystals for channeling experiments

(Davide De Salvador, Alberto Carnera)
The maturated experience in crystals manipulation and characterization is the basis for an exotic application: bend crystals can be used to steer accelerated beams even in ultra-relativistic regime; this has application for accelerators technology and radiation production. The group builds and tests bent crystalline devices especially in Germanium and run dedicate experiments at LNL, and in the framework of national and international collaborations at University of Mainz (MAMI) and CERN.


Nitrides

(Andrea Gasparotto)
Gallium Nitride (GaN)and other III-N compounds like InGaN and AlGaN has become important strategic materials thanks to their properties. They are currently used to fabricate light emitting devices (LED and Lasers) in the visible region of the light spectrum and control and power electronic devices. Research on nitride materials is very active aiming to improve efficiency and reliability of these devices. Among others the following aspects are currently being investigated:
-    Diffusion mechanisms of acceptor dopant (Mg) due to high temperature or high current density treatments.
-    Doping profiles of C and Fe used for semi-insulating buffer compensation
-    Ion implantation and activation of Mg and C for doping and device isolation.


Tailoring thermal expansion

(Andrea Sanson, Alberto Carnera)
Thermal expansion is critical in many technological applications and its control represents a challenge for the material design. The most promising route to achieve the control of thermal expansion is the use of non-conventional materials with Negative Thermal Expansion (NTE) properties. The group studies the physical phenomena connected to NTE and, in collaboration with the University of Science and Technology Beijing, the possible methods to control thermal expansion, like chemical intercalation, chemical substitution, nano-size effects.


Charge transport in ferroelectric oxides

(Marco Bazzan, Davide De Salvador)
Compared to other technological materials, our understanding of the charge photogeneration and transport mechanisms in ferroelectric oxides is still quite limited and yet very essential for a number of important applications, ranging from nonlinear optics to solar energy harvesting. The research activity in this field is devoted to the experimental and theoretical investigation of the self-localization and motion of charge carriers (polarons) mainly in ferroelectric Lithium Niobate by preparing samples with tailored characteristics, analyzing them by electrical and optical methods and modelling the obtained results.


Mode Mismatch sensing for gravitational interferometers

(Marco Bazzan)
The next generation of interferometers for gravitational waves detection will be operated using nonclassical light states (“squeezed” light) to improve their sensitivity. However, this kind of light is extremely sensitive to optical losses, which quickly degrade its useful properties. One of the major sources of optical losses is the imperfect matching between the optical field circulating in the interferometer and the modes of the different cavities inside it. This research activity, carried out in collaboration with the INFN Virgo PD-TN group, is devoted to the development of a new type of electro-optical sensor for mode mismatch monitoring and providing a feedback signal that will be used to cancel it out.