The HMMBE (High Mobility Molecular Beam Epitaxy) lab is a facility for the synthesis of high quality quantum-engineered compound semiconductor systems and devices.
The High Mobility Molecular Beam Epitaxy is a facility dedicated to the growth of high purity III/V semiconductors in ultra-high vacuum with atomic layer control on compositions and thicknesses.
The model is a Veeco Gen II machine with a dedicated design for high mobility, equipped with As (2X), Ga (2X), Al, In effusion cells and Si and C doping sources for growth on 2” GaAs wafers. Grown structures range from high mobility two-dimensional electron systems in GaAs/AlGaAs (with mobilities up to the 107cm2/Vs range) and metamorphic In0.75Ga0.25As/ In0.75Al0.25As heterostructures (with mobilities up to the 5X105 cm2/Vs), to photonic structures and self-assembled nanostructures. A multi-wavelength optical process monitor allows accurate real-time control of substrate temperature and growth rate with <1% accuracy through interference measurements.
The facility is completed by a variable temperature Cryogenic closed-cycle cryostat for magnetotransport, electro-optical and magneto-optical characterization (T in the 1.5 –400 K range, magnetic field up to 9 T), and magnetometry (vibrating magnetometer and AC susceptibility) up to 700K.
Instrumentation: A customized silicon source based on direct heating of a Si stripe by DC current has been developed in collaboration with the IOM technical services.
A collaboration with Elettra is aimed at the development of X-ray photon beam detectors based on GaAs avalanche photodiodes which, if successful, will find wide application in new generation light sources.
We are currently carrying out major upgrades involving new infrastructure and improvement of the current instrumentation data acquisition capabilities. The aim is to perform a complete record of all the instrumentation present. This process will enable, among other things, analysis by machine learning algorithms for carrying out predictive maintenance of the apparatus.
Software: The control software of the MBE machine has been developed in-house on a LabView platform, allowing flexibility in adding/adapting new sources and equipment.
A new ontology for sample growth is being developed in collaboration with Fondazione Bruno Kessler. This, together with the instrumentation upgrades, will allow for growth data to be stored in a Fair way on a local NOMAD Oasis. With such upgrades, we will both improve cross-lab reproducibility, and be able to use machine learning algorithms to optimize sample recipes.
The activity of the group is based on the development of high purity III/V semiconductors, with areas of application ranging from quantum computation to nanophotonics, spintronics and detectors.
We are part of consortia devoted to establishing the foundations of radically new solid-state platforms for fault tolerant, scalable quantum computation. Implementations range from high-fidelity qubit based on the Kitaev Chain to Andreev qubits in hybrid nanodevices and photonic quantum information processing. The first two technologies are implemented on interfaces between superconductors and semiconductor nanostructures. In particular, high quality metamorphic InAs-based quantum wells coupled to aluminum superconducting thin films formed in situ. The third one relies on 2-dimensional cluster states in site-controlled semiconductor quantum dot (QD) “molecules” realized in pyramidal structures on (111)B GaAs.
Another activity concerns the development of GaAs/AlGaAs multiple QW systems for applications in Mid-IR quantum cavity electrodynamics. This allows the manipulation of light-matter interactions through strong coupling between photonic density of states and QW intersubband excitonic transitions giving rise to cavity polaritons. Applications range from fundamental studies of condensation phenomena in electronic systems, to ultrafast devices for next-generation optical information technology such as Mid-IR bosonic lasers.
Finally, a collaboration with Elettra Sincrotrone Trieste within a PRIN 2022 project is aimed at the realization of X-ray detectors with high photon absorption, fast response times, resistance to radiation damage and RT operation. Detectors based on GaAs avalanche photodiodes are developed for applications in next-generation light sources (high brilliance synchrotron radiation and free electron lasers), high energy physics and medical imaging.
