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Two-dimensional transition metal dichalcogenide (TMD) semiconductors have risen as an important material class for novel nanoelectronic applications. Molybdenum disulfide (MoS2) is the most representative TMD compound due to its superior stability and attractive properties for (opto-) electronic devices. However, the synthesis of single-crystalline and functional MoS2 across large-area substrates remains crucial for its successful integration in semiconductor industry platforms. Therefore, this work focuses on the study of MoS2 epitaxy via two well-established industry-compatible synthesis methods, promising for the large-area and single-crystalline integration of van der Waals (vdW) materials. These methods are molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) and have studied MoS2 quasi-vdW heteroepitaxy on reconstructed sapphire substrates and MoS2 vdW homoepitaxy on exfoliated MoS2 flakes. By examining the MoS2 structural properties using diffraction and spectroscopy techniques, the epitaxial relation and crystal quality are assessed, which reveals insights into the prevalence of inter- and intragrain defects such as grain boundaries and sulfur vacancies. The MBE method yields superior epitaxial MoS2 registry on both sapphire and MoS2 surfaces as compared to MOVPE, although inferior defectivity arises from the typical lower MBE growth temperature and chalcogen partial pressure. Moreover, both synthesis methods generate high densities of twinned MoS2 grain boundaries, which hamper defect-free integration. As a result, this challenging integration might become an important bottleneck for industrial TMD-based applications with a low tolerance for material defects.

High quality GaAs is selectively grown in 40 nm width Shallow Trench Isolation patterned structures. The patterned wafers have a V-shape Si (111) surface obtained by Tetramethylammonium hydroxide etching. By employing a SiCoNi™ pre-epi clean and two-step growth procedure (low temperature buffer and high temperature main layer), defects are effectively confined at the trench bottom, leaving a dislocation-free GaAs layer at the upper part. The high crystal quality is confirmed by transmission electron microscopy. Scanning spreading resistance microscopy indicates a high resistance of GaAs. The process conditions and GaAs material quality are highly compatible with Si technology platform.

Spectroscopy of internal photoemission of electrons from Ge and Ge1−xSnx (x ≤ 0.08) alloys into amorphous Al2O3 is used to evaluate the energy of the semiconductor valence band top. It is found that in Ge and Ge1−xSnx the valence bands are aligned within the measurement accuracy (±0.05 eV) irrespective of the strain imposed on the semiconductor or by the kind of passivating inter-layer applied between the semiconductor and alumina. This indicates that the Ge1−xSnx-stressor approach may be useful for strain engineering in p-channel Ge metal-oxide-semiconductor transistors.

Tuning the desorption temperature of an As cap layer allows to achieve In0.53Ga0.47As(001) surfaces with (2 x 4) and (4 x 2) reconstructions which exhibit different chemical reactivity upon exposure in atmospheric pressure. Trimethyl-Al based atomic layer deposition of Al2O3 films on the two exposed surfaces causes a non-equivalent interface composition. This behavior is associated with a worse electrical quality of the interface with the exposed (4 x 2) In0.53Ga0.47As reconstruction. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3659688] We acknowledge grant from ARAMIS Project and M. Alia (MDM) for metal gate deposition

In this letter, we propose an atmospheric pressure-chemical vapor deposition technique to grow metastable GeSn epitaxial layers on Ge. We report the growth of defect free fully strained undoped and in-situ B doped GeSn layers on Ge substrates with Sit contents up to 8%. Those metastable layers stay fully strained after 30 min anneal in N-2 at 500 degrees C.; Ge-Sn interdiffusion is seen at 500 degrees C but not at lower temperature. B is 100% active in the in-situ GeSn:B layers up to a concentration of 1.7 x 10(19) cm(-3). GeSn:B provides slightly lower Hall hole mobility values than in pure p-type Ge especially for low B concentrations. (C) 2011 American Institute of Physics [doi.10.1063/1.3645620]

The efficiency of the ammonium sulfide vapor (ASV) treatment, as opposed to the wet treatment in the liquid ammonium sulfide solution, on the performance improvement of the In0.53Ga0.47As surface-channel as well as InP-capped buried-channel metal-oxide-semiconductor field-effect-transistors (MOSFET) was demonstrated for the first time. MOSFETs were fabricated with either HCl or ASV surface treatments prior to the gate oxide deposition. ASV treatment was found to be very efficient in boosting the drive current of the transistors compared to that of the HCl treatment. It was also found that the ASV treatment leads to a lower border trap density and slightly higher oxide/semiconductor interface defect density compared to that of the HCl treatment. X-ray photoelectron spectroscopy (XPS) studies of In0.53Ga0.47As native oxide regrowth after both surface treatments identified indium sub-oxides as a possible cause of the performance degradation of the HCl treated devices. Based on this work, ASV treatment could be an efficient solution to the passivation of III-V surfaces. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3638492] The authors acknowledge the European Commission for financial support in the DualLogic project no. 214579. Further, we thank the IMEC core partners within the IMEC’s Industrial Affiliation Program on Logic/Ge-III/V.

Experiments on internal photoemission of electrons from Si and TiNx into thin Al2O3 layers suggest that crystallization of amorphous Al2O3 to the cubic γ-Al2O3 is accompanied by only a ≈ 0.5 eV upshift of the conduction band bottom edge. As it is known that in transforming from the amorphous to the γ-phase, the bandgap of Al2O3 increases from 6.2 eV to 8.7 eV, more than 80% of this gap widening must occur at the VB side of the gap. The latter suggests that interaction between electron states of O anions plays the dominant role in the oxide gap widening.

We investigated the molecular beam deposition of Al2O3 on Ge0.95Sn0.05 surface with and without an ultra thin Ge cap layer in between. We first studied the atomic configuration of both Ge1−xSnx and Ge/Ge1−xSnx surfaces after deoxidation by reflection high-energy electron diffraction and resulted, respectively, in a c(4×2) and (2×1) surface reconstructions. After in situ deposition of an Al2O3 high-κ gate dielectric we evidenced using time-of-flight secondary ion mass spectroscopy analyses that Sn diffusion was at the origin of high leakage current densities in the Ge1−xSnx/Al2O3 gate stack. This damage could be avoided by inserting a thin 5-nm-thick Ge cap between the oxide and the Ge1−xSnx layer. Finally, metal-oxide-semiconductor capacitors on the Ge capped sample showed well-behaved capacitance-voltage (C-V) characteristics with interface trap density (Dit) in the range of 1012 eV−1 cm−2 in mid gap and higher close to the valence band edge.