117 research outputs found
Dynamic formation of spherical voids crossing linear defects
A predictive model for the evolution of porous Ge layer upon thermal
treatment is reported. We represent an idealized etched dislocation core as an
axially symmetric elongated hole and computed its dynamics during annealing.
Numerical simulations of the shape change of a completely spherical void via
surface diffusion have been performed. Simulations and experiments show
individual large spherical voids, aligned along the dislocation core. The
creation of voids could facilitate interactions between dislocations, enabling
the dislocation network to change its connectivity in a way that facilitates
the subsequent annihilation of dislocation segments. This confirms that
thermally activated processes such as state diffusion of porous materials
provide mechanisms whereby the defects are removed or arranged in
configurations of lower energy. This model is intended to be indicative, and
more detailed experimental characterization of process parameters such as
annealing temperature and time, and could estimate the annealing time for given
temperatures, or vice versa, with the right parameters.Comment: 7 pages, 3 figure
Deep germanium etching using time multiplexed plasma etching
Abstract : There is a growing need for patterning germanium for photonic and photovoltaics applications.
In this paper, the authors use a time multiplexed plasma etch process (Bosch process) to deep
etch a germanium substrate. They show that germanium etching presents a strong aspect ratio
dependent etching and that patterns present scallops mostly on the upper part (aspect ratio below
0.8). Passivation layers are formed during the passivation step by neutrals’ deposition and are
reinforced during the etching step by the redeposition of sputtered fluorocarbon species from the
etch front. When the sidewalls are passivated, reactive neutrals diffuse through Knudsen-like
diffusion down to the bottom of the pattern to etch the germanium. The Knudsen-like diffusion
is responsible for the aspect ratio dependent etching and makes difficult the etching of holes
with aspect ratios above 10 while trenches with aspect ratio of 17 are still etched faster than
2 lm/min
Optical modes at the interface between two dissimilar discrete meta-materials
We have studied theoretically and experimentally the properties of optical surface modes at the hetero-interface between two meta-materials. These meta-materials consisted of two 1D AlGaAs waveguide arrays with different band structures
Critical process temperatures for resistive InGaAsP/InP heterostructures heavily implanted by Fe or Ga ions
We report on critical ion implantation and rapid thermal annealing (RTA) process temperatures that produce resistive Fe- or Ga-implanted InGaAsP/InP heterostructures. Two InGaAsP/InP heterostructure compositions, with band gap wavelengths of 1.3 μm and 1.57 μm, were processed by ion implantation sequences done at multiple MeV energies and high fluence (1015 cm−2). The optimization of the fabrication process was closely related to the implantation temperature which influences the type of implant-induced defect structures. With hot implantation temperatures, at 373 K and 473 K, X-ray diffraction (XRD) revealed that dynamic defect annealing was strong and prevented the amorphization of the InGaAsP layers. These hot-implanted layers were less resistive and RTA could not optimize them systematically in favor of high resistivity. With cold implantation temperatures, at 83 K and even at 300 K, dynamic annealing was minimized. Damage clusters could form and accumulate to produce resistive amorphous-like structures. After recrystallization by RTA, polycrystalline signatures were found on every low-temperature Fe- and Ga-implanted structures. For both ion species, electrical parameters evolved similarly against annealing temperatures, and resistive structures were produced near 500 °C. However, better isolation was obtained with Fe implantation. Differences in sheet resistivities between the two alloy compositions were less than band gap-related effects. These observations, related to damage accumulation and recovery mechanisms, have important implications for the realization ion-implanted resistive layers that can be triggered with near infrared laser pulses and suitable for ultrafast optoelectronics
Hybrid MBE-CBE Growth and Characterization of undoped In 0,53 Ga 0,47 As on Fe-InP(001) for avalanche photodiodes (APDs)
International audienc
Wafer-scale detachable monocrystalline Germanium nanomembranes for the growth of III-V materials and substrate reuse
Germanium (Ge) is increasingly used as a substrate for high-performance
optoelectronic, photovoltaic, and electronic devices. These devices are usually
grown on thick and rigid Ge substrates manufactured by classical wafering
techniques. Nanomembranes (NMs) provide an alternative to this approach while
offering wafer-scale lateral dimensions, weight reduction, limitation of waste,
and cost effectiveness. Herein, we introduce the Porous germanium Efficient
Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of
wafer-scale detachable monocrystalline Ge NMs on porous Ge (PGe) and substrate
reuse. We demonstrate monocrystalline Ge NMs with surface roughness below 1 nm
on top of nanoengineered void layer enabling layer detachment. Furthermore,
these Ge NMs exhibit compatibility with the growth of III-V materials.
High-resolution transmission electron microscopy (HRTEM) characterization shows
Ge NMs crystallinity and high-resolution X-ray diffraction (HRXRD) reciprocal
space mapping endorses high-quality GaAs layers. Finally, we demonstrate the
chemical reconditioning process of the Ge substrate, allowing its reuse, to
produce multiple free-standing NMs from a single parent wafer. The PEELER
process significantly reduces the consumption of Ge during the fabrication
process which paves the way for a new generation of low-cost flexible
optoelectronics devices.Comment: 17 pages and 6 figures along with 3 figures in supporting informatio
Chemical composition of nanoporous layer formed by electrochemical etching of p-type GaAs
Abstract : We have performed a detailed characterization study of electrochemically etched p-type GaAs in a hydrofluoric acid-based electrolyte. The samples were investigated and characterized through cathodoluminescence (CL), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that after electrochemical etching, the porous layer showed a major decrease in the CL intensity and a change in chemical composition and in the crystalline phase. Contrary to previous reports on p-GaAs porosification, which stated that the formed layer is composed of porous GaAs, we report evidence that the porous layer is in fact mainly constituted of porous As2O3. Finally, a qualitative model is proposed to explain the porous As2O3 layer formation on p-GaAs substrate
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