S. Dunand

Plastic and Elastic Strain Fields in GaAs/Si Core-Shell Nanowires

Thanks to their unique morphology, nanowires have enabled integration of materials in a way that was not possible before with thin film technology. In turn, this opens new avenues for applications in the areas of energy harvesting, electronics, and optoelectronics. This is particularly true for axial heterostructures, while core-shell systems are limited by the appearance of strain-induced dislocations. Even more challenging is the detection and understanding of these defects. We combine geometrical phase analysis with finite element strain simulations to quantify and determine the origin of the lattice distortion in core-shell nanowire structures. Such combination provides a powerful insight in the origin and characteristics of edge dislocations in such systems and quantifies their impact with the strain field map. We apply the method to heterostructures presenting single and mixed crystalline phase. Mixing crystalline phases along a nanowire turns out to be beneficial for reducing strain in mismatched core-shell structures.

Hybrid axial and radial Si–GaAs heterostructures in nanowires

Hybrid structures are formed from materials of different families. Traditionally, group IV and III-V semiconductors have not been integrated together in the same device or application. In this work we present a new approach for obtaining Si-GaAs hybrid heterostructures in nanowires based on a combination of molecular beam epitaxy and plasma enhanced chemical vapor deposition. Crystalline Si segments are integrated into GaAs nanowires grown by the Ga-assisted growth method at temperatures as low as 250 °C. We find that one of the most important factors leading to the successful growth of Si segments on GaAs is the silane-hydrogen dilution, which affects the concentration of silicon and hydrogen-based radicals (SiHx with x < 3) in the plasma, and determines if the Si shell is amorphous, polycrystalline or crystalline, and also if the growth takes place in the axial and/or radial directions. This work opens the path for the successful integration of silicon and III-V materials in one single nanowire.

Image Sensors Based on Thin-film on CMOS Technology: Additional Leakage Currents due to Vertical Integration of the a-Si:H Diodes

Note: IMT-NE Number: 437 Reference PV-LAB-CONF-2006-010 Record created on 2009-02-10, modified on 2017-05-10

Performance analysis of a-Si:H detectors deposited on CMOS chips

Note: IMT-NE Number: 389 Reference PV-LAB-CONF-2004-012 Record created on 2009-02-10, modified on 2017-05-10

Micro-Channel Plate Detectors Based on Hydrogenated Amorphous Silicon

A new type of micro-channel plate detector based on hydrogenated amorphous silicon is proposed which overcomes the fabrication and performance issues of glass or bulk silicon ones. This new type of detectors consists in 80-100 µm thick layers of amorphous silicon which are micro-machined by deep reactive ion etching to form the channels. This paper focuses on the structure and fabrication process and presents first results obtained with test devices on electron detection which demonstrate amplification effects. Fabrication and performance issues are also discussed.

Vertically Integrated Amorphous Silicon Particle Sensors

Note: IMT-NE Number: 388 Reference PV-LAB-CONF-2004-018 Record created on 2009-02-10, modified on 2017-05-10

Radiation hard amorphous silicon particle sensors

Note: IMT-NE Number: 409 Reference PV-LAB-CONF-2005-016 Record created on 2009-02-10, modified on 2017-05-10