Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GaSb”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

GaSb-based heterostructure with buried vacuum pocket photonic crystal layer

The vacuum pocket retaining molecular beam epitaxial regrowth of the nano-patterned GaSb surface was demonstrated. The high contrast 2D photonic crystal layer was incorporated into the test 2 μm emitting laser heterostructure. The photonic dispersion determined from angle-resolved electroluminescence experiment showed four well-resolved bands corresponding to the model predictions for the square lattice. The single-mode lasing near 2 μm has been observed at the temperature corresponding to the alignment of the photonic crystal band-edge states and the quantum well gain peak. The reference devices without the photonic crystal layer emitted trivial spectra and did not lase at any temperature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Continuous wave room temperature operation of the 2 $μ$m GaSb-based photonic crystal surface emitting diode lasers

Continuous wave room temperature operation of 2 μm GaSb-based photonic-crystal surface-emitting diode lasers has been realized. The deep etched square mesa devices showed threshold current densities of 500 A/cm 2 at 20 °C. The epi-side down mounted lasers generated above 10 mW of output power in the continuous wave regime and tens of milliwatts in pulses from the 200 × 200 μm 2 aperture. Here, the breakthrough in the device performance parameters was achieved thanks to a highly homogeneous air-pocket retaining epitaxial regrowth process optimized for a specifically designed antimonide diode laser heterostructure. The nanofabrication method utilizing low temperature atomic hydrogen surface cleaning yielded low disorder square lattice of droplet-shaped voids covered by uniform p-cladding layer. The laser emission spectrum as well as near/far field patterns demonstrated peculiar features presumably linked to deformation of the void shape during regrowth and formation of the array of filaments.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Molecular beam epitaxy growth and optoelectronic properties of droplet-free lattice-matched GaInAsSbBi on GaSb with wavelength extension exceeding 5 μ m

GaInAsSbBi alloys are grown lattice-matched on GaSb by molecular beam epitaxy demonstrating smooth surface morphologies, >5 μm wavelength photoluminescence emission, and minority carrier lifetimes >1 μs. At a growth temperature of 400 °C, the Ga flux is systematically increased and the Bi flux systematically decreased to identify GaInAsSbBi growth conditions that yield smooth droplet-free surface morphologies. The minority carrier lifetime is evaluated using time-resolved photoluminescence, where it is observed that GaInAsSbBi samples exhibit minority carrier lifetimes comparable to their Bi-free GaInAsSb counterparts, on the order of 1.5–2 μs. The bandgap and Urbach energy are evaluated from steady-state photoluminescence to gain insight into the impact of the incorporated Bi. Coupled with Rutherford backscattering spectrometry measurements of the Bi mole fraction, bandgap reduction rates of 97 meV/% Bi in InAsSbBi and 150 meV/% Bi in GaInAsSbBi are observed, significantly higher than previous evaluations in InAsSbBi (35–55 meV/% Bi). Detailed comparisons of the Bi mole fraction, bandgap energy, and Urbach energy indicate that the bandgap reduction potential in this alloy system is inhibited by the formation of Bi clusters; however, the inclusion of Ga in the quinary alloy is effective in suppressing Bi's tendency to incorporate in clusters for Ga mole fractions >9%, maximizing the bandgap reduction per unit Bi and overall optoelectronic quality.

Atomic force microscopy↗
DOE OSTI2024

Photonic Crystal Surface Emitting GaSb-Based Type-I Quantum Well Diode Lasers

The GaSb-based epitaxially regrown monolithic diode PCSELs operating near 2 μm at room temperature in continuous wave regime and generating 30 mW of output power from 200 μm diameter aperture have been designed and fabricated. Here, the devices demonstrated CW threshold current density of about 500 A/cm 2 . The laser output power was enhanced thanks to increased buried void area fill-factor in the photonic crystal layer with multiple voids per unit cell. The PCSEL generated ultra-low divergence donut shape beams at the currents near threshold. At higher injection currents, the device brightness was limited by excitation of the higher order lateral modes. Generation of the vector-vortex beams of different types by different band edge states of the buried photonic crystal was observed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Control of polymorphism during epitaxial growth of hyperferroelectric candidate LiZnSb on GaSb (111)B

A major challenge for ferroelectric devices is the depolarization field, which competes with and often destroys long-range polar order in the limit of ultrathin films. Recent theoretical predictions suggest a new class of materials, termed hyperferroelectics, that should be robust against the depolarization field and enable ferroelectricity down to the monolayer limit. Here, the authors demonstrate the epitaxial growth of hexagonal LiZnSb, one of the hyperferroelectric candidate materials, by molecular-beam epitaxy on GaSb (111)B substrates. Due to the high volatility of all three atomic species, they find that LiZnSb can be grown in an adsorption-controlled window, using an excess zinc flux. Within this window, the desired polar hexagonal phase is stabilized with respect to a competing cubic polymorph, as revealed by x-ray diffraction and transmission electron microscopy measurements. First-principles calculations show that for moderate amounts of epitaxial strain and moderate concentrations of Li vacancies, the cubic LiZnSb phase is lower in formation energy than the hexagonal phase, but only by a few millielectronvolts per formula unit. Therefore, they suggest that kinetics plays a role in stabilizing the desired hexagonal phase at low temperatures. Their results provide a path toward experimentally demonstrating ferroelectricity and hyperferroelectricity in a new class of ternary intermetallic compounds.

42 ENGINEERING↗
DOE OSTI2021

High-power narrow spectrum GaSb-based DBR lasers emitting near 2.1 µm

Stable high-power narrow-linewidth operation of the 2.05–2.1 µm GaSb-based diode lasers was achieved by utilizing the sixth-order surface-etched distributed Bragg reflector (DBR) mirrors. The DBR multimode devices with 100 µm wide ridge waveguides generated ~850 mW in the continuous wave (CW) regime at 20°C. The device CW output power was limited by thermal rollover. The laser emission spectrum was defined by Bragg reflector reflectivity at all operating currents in a wide temperature range. Finally, the devices operated at DBR line with detuning from gain peak exceeding 10 meV.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Optical and electrical properties of proton-implanted p -GaSb for electrical isolation

The effect of proton implantation as isolation implant and subsequent annealing on the optical absorption and electrical resistivity of low-bandgap p -GaSb is reported. The measured transmittance spectra indicates that implantation creates a distribution of energy levels extending into the bandgap. Electrical measurements show that the average sheet resistance of the implanted layer increases only by an order of magnitude from its pre-implantation value at a proton dose of ~10 13 cm -2 followed by 200 °C annealing. It is also shown that annealing reduces the implantation-induced optical absorption while still retaining a high electrical resistivity.

42 ENGINEERING↗
NASA NTRS1968

GaSb-ZnTe heterojunction.

GaSb-ZnTe heterojunction fabrication method, noting photoresponse, fluorescence and light transmission

Fischler, S.↗
NASA NTRS1977

Microstructure and composition of InSb-GaSb ingots directionally solidified aboard Skylab

InSb-GaSb solid solution ingots prepared by directional solidification aboard Skylab and on earth consist of twins with (111) twin planes parallel to the direction of solidification and growth directions that lie along 211, 110, or 321 crystallographic directions. Significant fractions of several ingots prepared aboard Skylab were solidified from melts that were not in contact with container walls, resulting in convection driven by surface tension gradients in the melt and corresponding radially-symmetric composition variations in the ingot. In these regions, adjacent twins exhibit marked differences in indium content, indicating a substantial dependence of composition on crystallographic orientation.

Lefever, R. A.↗
NASA NTRS1991

Radioisotope thermal photovoltaic application of the GaSb solar cell

An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach.

Morgan, M. D.↗
NASA NTRS1992

Solidification of InSb-GaSb alloy and InSb with vibration

The objective of this project is to determine the influence of vibration on the composition homogeneity and microstructure of alloy semiconductors solidified with the Vertical Bridgman-Stockbarger (VBS) technique. InSb-GaSb and InSb were directionally solidified in a VBS apparatus with axial vibration of the ampoule.

Yuan, Weijun↗
DOE OSTI2020

Materials Data on Ba(GaSb)2 by Materials Project

BaGa2Sb2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Ba–Sb bond distances ranging from 3.58–3.83 Å. In the second Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Ba–Sb bond distances ranging from 3.57–3.69 Å. There are four inequivalent Ga2+ sites. In the first Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three equivalent Sb3- atoms. There are two shorter (2.75 Å) and one longer (2.85 Å) Ga–Sb bond lengths. In the second Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are two shorter (2.73 Å) and one longer (2.82 Å) Ga–Sb bond lengths. In the third Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are one shorter (2.70 Å) and two longer (2.75 Å) Ga–Sb bond lengths. In the fourth Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are one shorter (2.74 Å) and two longer (2.77 Å) Ga–Sb bond lengths. There are four inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded in a 7-coordinate geometry to four Ba2+ and three Ga2+ atoms. In the second Sb3- site, Sb3- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Ga2+ atoms. In the third Sb3- site, Sb3- is bonded to three equivalent Ba2+ and three Ga2+ atoms to form distorted edge-sharing SbBa3Ga3 octahedra. In the fourth Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Ba2+ and three equivalent Ga2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GaSb)2 by Materials Project

EuGa2Sb2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Eu–Sb bond distances ranging from 3.39–3.47 Å. In the second Eu2+ site, Eu2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Eu–Sb bond distances ranging from 3.41–3.48 Å. In the third Eu2+ site, Eu2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Eu–Sb bond distances ranging from 3.39–3.47 Å. In the fourth Eu2+ site, Eu2+ is bonded in a 6-coordinate geometry to six Sb3- atoms. There are a spread of Eu–Sb bond distances ranging from 3.40–3.47 Å. There are eight inequivalent Ga2+ sites. In the first Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. All Ga–Sb bond lengths are 2.72 Å. In the second Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. All Ga–Sb bond lengths are 2.72 Å. In the third Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. All Ga–Sb bond lengths are 2.72 Å. In the fourth Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. All Ga–Sb bond lengths are 2.72 Å. In the fifth Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are two shorter (2.73 Å) and one longer (2.86 Å) Ga–Sb bond lengths. In the sixth Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are a spread of Ga–Sb bond distances ranging from 2.72–2.86 Å. In the seventh Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are two shorter (2.73 Å) and one longer (2.87 Å) Ga–Sb bond lengths. In the eighth Ga2+ site, Ga2+ is bonded in a trigonal non-coplanar geometry to three Sb3- atoms. There are a spread of Ga–Sb bond distances ranging from 2.72–2.87 Å. There are eight inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the second Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the third Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the fourth Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the fifth Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the sixth Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the seventh Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms. In the eighth Sb3- site, Sb3- is bonded in a 6-coordinate geometry to three Eu2+ and three Ga2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Carrier recombination dynamics and temperature dependent optical properties of InAs–GaSb heterostructures

Heterostructures with two dissimilar materials could offer unprecedented properties if one can carefully synthesize these heterostructures with atomically smooth interfaces and reduced number of recombination centers. InAs/GaSb-based heterostructures have technological importance for long wavelength infrared photodetectors if one can synthesize these materials with high-optical quality and high-carrier lifetime. In this work, the InAs/GaSb heterostructures with a different number of heterointerfaces and growth conditions were grown by solid source molecular beam epitaxy using valved cracker sources for both arsenic and antimony. Precise control of growth parameters and shutter sequences enabled abrupt InAs/GaSb heterointerfaces, as supported by a high-resolution transmission electron microscopic study. The temperature and power-dependent optical properties by photoluminescence (PL) spectroscopic analysis of InAs/GaSb heterostructures with 4 and 28 heterointerfaces displayed donor to the acceptor and the exciton bound to complex defects (V Ga Ga Sb ) 0 . Since the optical transition in PL measurements serves to determine the quality of the material, and the observed excitonic transitions from these InAs/GaSb heterostructures is an indication of high-quality materials. The high-carrier lifetimes of 139 ns to 185 ns from InAs/GaSb heterostructures were measured using microwave photoconductivity decay (μ-PCD) technique at room temperature. The observed increase in carrier lifetime is due to the decreasing number of Ga-related carrier recombination centers or defect complexes. This is further supported by the PL spectroscopic study. In addition, the carrier lifetime with different injection levels is supported by Shockley–Read–Hall recombination. We report these InAs/GaSb heterostructures with high-optical quality and high-carrier lifetimes would offer a path for the development of high-performance infrared photodetectors.

36 MATERIALS SCIENCE↗