The monolithic integration of III-V semiconductors on silicon and particularly of GaAs has aroused great interest since the 1980s. Potential applications are legion, ranging from photovoltaics to high mobility channel transistors. By using a novel integration method, we have shown that it is possible to achieve heteroepitaxial integration of GaAs crystals (typical size 1 μm) on silicon without any structural defect such as antiphase domains, dislocations, or stress, usually reported for direct GaAs heteroepitaxy on silicon. However, concerning their electronic properties, conventional free carrier characterization methods are impractical due to the micrometric size of GaAs crystals. In order to evaluate the GaAs material quality for optoelectronic applications, a series of indirect analyses such as atom probe tomography, Raman spectroscopy, and micro-photoluminescence as a function of temperature were performed. These revealed a high content of partially electrically active carbon originating from the trimethylgallium used as the Ga precursor. Nevertheless, the very good homogeneity observed by this doping mechanism and the attractive properties of carbon as a dopant once controlled to a sufficient degree are a promising route to device doping.

An innovative approach is being investigated to develop III–V compounds on silicon (Si) substrates with the purpose to offer a technological alternative for the development of high efficiency solar cells ( ∼ 30 %). Until now, germanium (Ge) substrate has been the privileged material for the development of III–V multi-junctions (MJ) solar cells mainly dedicated to space applications. Ge offers several advantages, namely the lattice matching to Si and its use as a bottom cell in the MJ. However, the main drawback remains the cost of Ge substrates, which makes it inappropriate for terrestrial photovoltaic (PV) applications. New routes for high efficiency MJ solar cells are expected through the significant improvements of the selective area epitaxy (Li et al., J Appl Phys 103:106102, 2008; Deura et al., J Cryst Growth 310:4768–4771, 2008; Hsu et al., Appl Phys Lett 99:133115, 2011) allowing defect free III–V compounds to be grown on Si substrates patterned with dielectric films. In this work, Si nanoscale areas opened through a SiO2 layer ( < 1 nm) formed on (001) Si have been used to grow GaAs microcrystals by chemical beam epitaxy (CBE) in the temperature range 550–600 ∘C (Renard et al., Appl Phys Lett 102:191915, 2013). Structural, optoelectronic and electrical properties of GaAs microcrystals have been analyzed at room temperature by micro-Raman, photoluminescence and conductive probe atomic force microscopy (CP-AFM). The fine structure of crystals (facet orientations, crystal defects) has also been investigated by transmission electron microscopy (TEM). Linear polarized Raman spectroscopy performed on multiple microcrystals shows exclusively the TO mode which is typically expected for (110) GaAs plane orientations and/or heavily n-type Si-doped GaAs (Zardo et al., Phys Rev B 80:245324, 2009). TEM confirms that all facets are {110}, but unintentionally Si doping cannot be excluded. Indeed, PL measure-ments point out a red shift for the microcrystals for which nucleation seeds were created by silane exposure. CP-AFM imaging of GaAs microcrystals performed at + 1 and − 1 V, respectively, points out a current rectification behavior confirmed by local I–V measure-ments (Fig. 37.1). These results can be interpreted as a sign of the presence of a p-n junction, which agrees well with the p-type doping of Si substrates used in this study (1–5 Ωcm) and the unintentionally n-type doping of GaAs microcrystals suggested by PL measurements (Pavesi and Henini, Microelectron J 28:717–726, 1997).

High quality micrometer scale GaAs crystals were grown by chemical beam epitaxy from nanoscale Si seeds on a 0.6 nm thick SiO2 layer formed on S (001). The use of small diameter openings is expected to lead to a dislocation-free relaxation and to the reduction of the antiphase defects. Thus, the so-formed GaAs crystals are found to be completely relaxed and antiphase boundaries free. The lateral epitaxy without misfit dislocation can evolve on the SiO2 layer that prevents the Si substrate from imposing its lattice parameter on the GaAs crystal. The effect of the growth temperature on the GaAs crystal materials quality was particularly studied by transmission electron microscopy and it-Raman. (C) 2014 Elsevier B.V. All rights reserved.

The epitaxial lateral overgrowth of microscale GaAs crystals on a 0.6 nm thick SiO2 layer from nanoscale Si seeds is investigated in order to develop GaAs monolithic hetero-epitaxy onto (001) Si. The nucleation from small width openings enables to avoid the emission of misfit dislocations and the formation of antiphase domains. Consequently, the interface between the GaAs island and the SiO2 layer remains perfectly sharp and free of defects. The only defects found by transmission electron microscopy in each island are pairs of twins, and a simple model based on the anisotropy of zinc blende crystal is proposed to explain their formation. Micro-photoluminescence measurements performed at room temperature show that these twins are not detrimental for the quality of microscale GaAs crystals.

Because of major advantages (e.g. weight saving, maintenance advantages), the airframe manufacturers use more and more Polymer Matrix Composites (PMCs) in different parts of aircraft structures. But PMCs have a substantial disadvantage of low conductivity and therefore low Electromagnetic (EM) Shielding. Electromagnetic Interference (EMI) sources are all around and inside aircraft and can potentially threat the immunity of aircraft. Metallic meshes have been used to overcome this shortage. However in high frequencies most of the mentioned methods loose their performances. Regrettably on one side most of the present and upcoming systems onboard of aircraft are functional in mentioned range of frequencies. On the other side, passengers use more and more Personal Electronic Devices (PEDs) onboard of aircraft. Interferences caused by PEDs are also in the same range of frequencies. Measured susceptibility caused by PEDs is higher in composite aircrafts comparing to metallic ones. To overcome this back door lack of composite aircrafts, design of a new light weight shield particularly for aeronautic application is needed. Metallic nanoparticles have a great potential to be used as new EM shields for aerospace applications, particularly in high frequencies. Without multidisciplinary characterization of new shield, the application onboard would be suspended. Here the encouraging results of EM characterization are presented. Thermal, microscopy and mechanical tests are also performed. Based on acquired results in this work, thermal and mechanical behaviors as well as distribution of particles are all acceptable. The promising results obtained in this work can assure the designers on using metallic nanoparticles as a new shield for protection of composite aircrafts.

To date, high efficiency multijunction solar cells have been developed on Ge or GaAs substrates for space applications, and terrestrial applications are hampered by high fabrication costs. In order to reduce this cost, we propose a breakthrough technique of III-V compound heteroepitaxy on Si substrates without generation of defects critical to PV applications. With this technique we expect to achieve perfect integration of heterogeneous Ga1-xInxAs micro-crystals on Si substrates. In this paper, we show that this is the case for x=0. GaAs crystals were grown by Epitaxial Lateral Overgrowth on Si (100) wafers covered with a thin SiO2 nanostructured layer. The cristallographic structure of these crystals is analysed by MEB and TEM imaging. Micro-Raman and Micro-Photomuminescence spectra of GaAs crystals grown with different conditions are compared with those of a reference GaAs wafer in order to have more insight on eventual local strains and their cristallinity. This work aims at developping building blocks to further develop a GaAs/Si tandem demonstrator with a potential conversion efficiency of 29.6% under AM1.5G spectrum without concentration, as inferred from our realistic modeling. This paper shows that Epitaxial Lateral Overgrowth has a very interesting potential to develop multijunction solar cells on silicon approaching the today 30.3% world record of a GaInP/GaAs tandem cell under the same illumination conditions, but on a costlier substrate than silicon.