138,445 research outputs found
High efficiency InGaAs solar cells on Si by InP layer transfer
InP/Si substrates were fabricated through wafer bonding and helium-induced exfoliation of InP, and InGaAs solar cells lattice matched to bulk InP were grown on these substrates using metal-organic chemical-vapor deposition. The photovoltaic characteristics of the InGaAs cells fabricated on the wafer-bonded InP/Si substrates were comparable to those synthesized on commercially available epiready InP substrates, thus providing a demonstration of wafer-bonded InP/Si substrates as an alternative to bulk InP substrates for solar cell applications
InGaAs/InP double heterostructures on InP/Si templates fabricated by wafer bonding and hydrogen-induced exfoliation
Hydrogen-induced exfoliation combined with wafer bonding has been used to transfer ~600-nm-thick films of (100) InP to Si substrates. Cross-section transmission electron microscopy (TEM) shows a transferred crystalline InP layer with no observable defects in the region near the bonded interface and an intimately bonded interface. InP and Si are covalently bonded as inferred by the fact that InP/Si pairs survived both TEM preparation and thermal cycles up to 620 °C necessary for metalorganic chemical vapor deposition growth. The InP transferred layers were used as epitaxial templates for the growth of InP/In0.53Ga0.47As/InP double heterostructures. Photoluminescence measurements of the In0.53Ga0.47As layer show that it is optically active and under tensile strain, due to differences in the thermal expansion between InP and Si. These are promising results in terms of a future integration of Si electronics with optical devices based on InP-lattice-matched materials
Electronic structure of self-assembled InAs/InP quantum dots: A Comparison with self-assembled InAs/GaAs quantum dots
We investigate the electronic structure of the InAs/InP quantum dots using an
atomistic pseudopotential method and compare them to those of the InAs/GaAs
QDs. We show that even though the InAs/InP and InAs/GaAs dots have the same dot
material, their electronic structure differ significantly in certain aspects,
especially for holes: (i) The hole levels have a much larger energy spacing in
the InAs/InP dots than in the InAs/GaAs dots of corresponding size. (ii)
Furthermore, in contrast with the InAs/GaAs dots, where the sizeable hole ,
intra-shell level splitting smashes the energy level shell structure, the
InAs/InP QDs have a well defined energy level shell structure with small ,
level splitting, for holes. (iii) The fundamental exciton energies of the
InAs/InP dots are calculated to be around 0.8 eV ( 1.55 m), about
200 meV lower than those of typical InAs/GaAs QDs, mainly due to the smaller
lattice mismatch in the InAs/InP dots. (iii) The widths of the exciton
shell and shell are much narrower in the InAs/InP dots than in the
InAs/GaAs dots. (iv) The InAs/GaAs and InAs/InP dots have a reversed light
polarization anisotropy along the [100] and [10] directions
On the Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers in a Magnetic Field
The InGaAs-InAlAs-InP high electron mobility transistor (InP HEMT) is the
preferred active device used in a cryogenic low noise amplifier (LNA) for
sensitive detection of microwave signals. We observed that an InP HEMT
0.3-14GHz LNA at 2K, where the in-going transistors were oriented perpendicular
to a magnetic field, heavily degraded in gain and average noise temperature
already up to 1.5T. Dc measurements for InP HEMTs at 2K revealed a strong
reduction in the transistor output current as a function of static magnetic
field up to 14T. In contrast, the current reduction was insignificant when the
InP HEMT was oriented parallel to the magnetic field. Given the transistor
layout with large gate width/gate length ratio, the results suggest a strong
geometrical magnetoresistance effect occurring in the InP HEMT. This was
confirmed in the angular dependence of the transistor output current with
respect to the magnetic field. Key device parameters such as transconductance
and on-resistance were significantly affected at small angles and magnetic
fields. The strong angular dependence of the InP HEMT output current in a
magnetic field has important implications for the alignment of cryogenic LNAs
in microwave detection experiments involving magnetic fields
Pushing indium phosphide quantum dot emission deeper into the near infrared
Cadmium-free near infrared (NIR) emitting quantum dots (QDs) have significant potential for multiplexed tissue-depth imaging applications in the first optical tissue window (i.e., 650 – 900 nm). Indium phosphide (InP) chemistry provides one of the more promising cadmium-free options for biomedical imaging, but the full tunability of this material has not yet been achieved. Specifically, InP QD emission has been tuned from 480 – 730 nm in previous literature reports, but examples of samples emitting from 730 nm to the InP bulk bandgap limit of 925 nm are lacking. We hypothesize that by generating inverted structures comprising ZnSe/InP/ZnS in a core/shell/shell heterostructure, optical emission from the InP shell can be tuned by changing the InP shell thickness, including pushing deeper into the NIR than current InP QDs. Colloidal synthesis methods including hot injection precipitation of the ZnSe core and a modified successive ion layer adsorption and reaction (SILAR) method for stepwise shell deposition were used to promote growth of core/shell/shell materials with varying thicknesses of the InP shell. By controlling the number of injections of indium and phosphorous precursor material, the emission peak was tuned from 515 nm to 845 nm (2.41 – 1.47 eV) with consistent full width half maximum (FWHM) values of the emission peak ~0.32 eV. To confer water solubility, the nanoparticles were encapsulated in PEGylated phospholipid micelles, and multiplexing of NIR-emitting InP QDs was demonstrated using an IVIS imaging system. These materials show potential for multiplexed imaging of targeted QD contrast agents in the first optical tissue window
Twinning superlattices in indium phosphide nanowires
Here, we show that we control the crystal structure of indium phosphide (InP)
nanowires by impurity dopants. We have found that zinc decreases the activation
barrier for 2D nucleation growth of zinc-blende InP and therefore promotes the
InP nanowires to crystallise in the zinc blende, instead of the commonly found
wurtzite crystal structure. More importantly, we demonstrate that we can, by
controlling the crystal structure, induce twinning superlattices with
long-range order in InP nanowires. We can tune the spacing of the superlattices
by the wire diameter and the zinc concentration and present a model based on
the cross-sectional shape of the zinc-blende InP nanowires to quantitatively
explain the formation of the periodic twinning.Comment: 18 pages, 4 figure
Nanoscale Defect Formation on InP(111) Surfaces after MeV Sb Implantation
We have studied the surface modifications as well as the surface roughness of
the InP(111) surfaces after 1.5 MeV Sb ion implantations. Scanning Probe
Microscope (SPM) has been utilized to investigate the ion implanted InP(111)
surfaces. We observe the formation of nanoscale defect structures on the InP
surface. The density, height and size of the nanostructures have been
investigated here as a function of ion fluence. The rms surface roughness, of
the ion implanted InP surfaces, demonstrates two varied behaviors as a function
of Sb ion fluence. Initially, the roughness increases with increasing fluence.
However, after a critical fluence the roughness decreases with increasing
fluence. We have further applied the technique of Raman scattering to
investigate the implantation induced modifications and disorder in InP. Raman
Scattering results demonstrate that at the critical fluence, where the decrease
in surface roughness occurs, InP lattice becomes amorphous.Comment: 18 pages, 9 figure
A Semiconductor Under Insulator Technology in Indium Phosphide
This Letter introduces a Semiconductor-Under-Insulator (SUI) technology in
InP for designing strip waveguides that interface InP photonic crystal membrane
structures. Strip waveguides in InP-SUI are supported under an atomic layer
deposited insulator layer in contrast to strip waveguides in silicon supported
on insulator. We show a substantial improvement in optical transmission when
using InP-SUI strip waveguides interfaced with localized photonic crystal
membrane structures when compared with extended photonic crystal waveguide
membranes. Furthermore, SUI makes available various fiber-coupling techniques
used in SOI, such as sub-micron coupling, for planar membrane III-V systems
Ultrafast trapping times in ion implanted InP
As⁺ and P⁺implantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1×10¹⁶ cm⁻² and p-type InP was implanted with doses between 1×10¹² and 1×10¹⁶ cm⁻². Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implantedp-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity
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