Matching Items (4)
Filtering by
- All Subjects: Semiconductors
- All Subjects: Bismides
Description
High-performance III-V semiconductors based on ternary alloys and superlattice systems are fabricated, studied, and compared for infrared optoelectronic applications. InAsBi is a ternary alloy near the GaSb lattice constant that is not as thoroughly investigated as other III-V alloys and that is challenging to produce as Bi has a tendency to surface segregate and form droplets during growth rather than incorporate. A growth window is identified within which high-quality droplet-free bulk InAsBi is produced and Bi mole fractions up to 6.4% are obtained. Photoluminescence with high internal quantum efficiency is observed from InAs/InAsBi quantum wells. The high structural and optical quality of the InAsBi materials examined demonstrates that bulk, quantum well, and superlattice structures utilizing InAsBi are an important design option for efficient infrared coverage.
Another important infrared material system is InAsSb and the strain-balanced InAs/InAsSb superlattice on GaSb. Detailed examination of X-ray diffraction, photoluminescence, and spectroscopic ellipsometry data provides the temperature and composition dependent bandgap of bulk InAsSb. The unintentional incorporation of approximately 1% Sb into the InAs layers of the superlattice is measured and found to significantly impact the analysis of the InAs/InAsSb band alignment. In the analysis of the absorption spectra, the ground state absorption coefficient and transition strength of the superlattice are proportional to the square of the electron-hole wavefunction overlap; wavefunction overlap is therefore a major design parameter in terms of optimizing absorption in these materials. Furthermore in addition to improvements through design optimization, the optical quality of the materials studied is found to be positively enhanced with the use of Bi as a surfactant during molecular beam epitaxy growth.
A software tool is developed that calculates and optimizes the miniband structure of semiconductor superlattices, including bismide-based designs. The software has the capability to limit results to designs that can be produced with high structural and optical quality, and optimized designs in terms of maximizing absorption are identified for several infrared superlattice systems at the GaSb lattice constant. The accuracy of the software predictions are tested with the design and growth of an optimized mid-wave infrared InAs/InAsSb superlattice which exhibits superior optical and absorption properties.
Another important infrared material system is InAsSb and the strain-balanced InAs/InAsSb superlattice on GaSb. Detailed examination of X-ray diffraction, photoluminescence, and spectroscopic ellipsometry data provides the temperature and composition dependent bandgap of bulk InAsSb. The unintentional incorporation of approximately 1% Sb into the InAs layers of the superlattice is measured and found to significantly impact the analysis of the InAs/InAsSb band alignment. In the analysis of the absorption spectra, the ground state absorption coefficient and transition strength of the superlattice are proportional to the square of the electron-hole wavefunction overlap; wavefunction overlap is therefore a major design parameter in terms of optimizing absorption in these materials. Furthermore in addition to improvements through design optimization, the optical quality of the materials studied is found to be positively enhanced with the use of Bi as a surfactant during molecular beam epitaxy growth.
A software tool is developed that calculates and optimizes the miniband structure of semiconductor superlattices, including bismide-based designs. The software has the capability to limit results to designs that can be produced with high structural and optical quality, and optimized designs in terms of maximizing absorption are identified for several infrared superlattice systems at the GaSb lattice constant. The accuracy of the software predictions are tested with the design and growth of an optimized mid-wave infrared InAs/InAsSb superlattice which exhibits superior optical and absorption properties.
ContributorsWebster, Preston Thomas (Author) / Johnson, Shane R (Thesis advisor) / Zhang, Yong-Hang (Committee member) / Menéndez, Jose (Committee member) / Vasileska, Dragica (Committee member) / Arizona State University (Publisher)
Created2016
Description
InAsBi is a narrow direct gap III-V semiconductor that has recently attracted considerable attention because its bandgap is tunable over a wide range of mid- and long-wave infrared wavelengths for optoelectronic applications. Furthermore, InAsBi can be integrated with other III-V materials and is potentially an alternative to commercial II-VI photodetector materials such as HgCdTe.
Several 1 μm thick, nearly lattice-matched InAsBi layers grown on GaSb are examined using Rutherford backscattering spectrometry and X-ray diffraction. Random Rutherford backscattering measurements indicate that the average Bi mole fraction ranges from 0.0503 to 0.0645 for the sample set, and ion channeling measurements indicate that the Bi atoms are substitutional. The X-ray diffraction measurements show a diffraction sideband near the main (004) diffraction peak, indicating that the Bi mole fraction is not laterally uniform in the layer. The average out of plane tetragonal distortion is determined by modeling the main and sideband diffraction peaks, from which the average unstrained lattice constant of each sample is determined. By comparing the Bi mole fraction measured by random Rutherford backscattering with the InAsBi lattice constant for the sample set, the lattice constant of zinc blende InBi is determined to be 6.6107 Å.
Several InAsBi quantum wells tensilely strained to the GaSb lattice constant with dilute quantities of Bi are characterized using photoluminescence spectroscopy. Investigation of the integrated intensity as a function of carrier excitation density spanning 5×1025 to 5×1026 cm-3 s-1 indicates radiative dominated recombination and high quantum efficiency over the 12 to 250 K temperature range. The bandgap of InAsBi is ascertained from the photoluminescence spectra and parameterized as a function of temperature using the Einstein single oscillator model. The dilute Bi mole fraction of the InAsBi quantum wells is determined by comparing the measured bandgap energy to that predicted by the valence band anticrossing model. The Bi mole fraction determined by photoluminescence agrees reasonably well with that estimated using secondary ion mass spectrometry.
Several 1 μm thick, nearly lattice-matched InAsBi layers grown on GaSb are examined using Rutherford backscattering spectrometry and X-ray diffraction. Random Rutherford backscattering measurements indicate that the average Bi mole fraction ranges from 0.0503 to 0.0645 for the sample set, and ion channeling measurements indicate that the Bi atoms are substitutional. The X-ray diffraction measurements show a diffraction sideband near the main (004) diffraction peak, indicating that the Bi mole fraction is not laterally uniform in the layer. The average out of plane tetragonal distortion is determined by modeling the main and sideband diffraction peaks, from which the average unstrained lattice constant of each sample is determined. By comparing the Bi mole fraction measured by random Rutherford backscattering with the InAsBi lattice constant for the sample set, the lattice constant of zinc blende InBi is determined to be 6.6107 Å.
Several InAsBi quantum wells tensilely strained to the GaSb lattice constant with dilute quantities of Bi are characterized using photoluminescence spectroscopy. Investigation of the integrated intensity as a function of carrier excitation density spanning 5×1025 to 5×1026 cm-3 s-1 indicates radiative dominated recombination and high quantum efficiency over the 12 to 250 K temperature range. The bandgap of InAsBi is ascertained from the photoluminescence spectra and parameterized as a function of temperature using the Einstein single oscillator model. The dilute Bi mole fraction of the InAsBi quantum wells is determined by comparing the measured bandgap energy to that predicted by the valence band anticrossing model. The Bi mole fraction determined by photoluminescence agrees reasonably well with that estimated using secondary ion mass spectrometry.
ContributorsShalindar Christraj, Arvind Joshua Jaydev (Author) / Johnson, Shane R (Thesis advisor) / Alford, Terry L. (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2016
Description
III-V-bismide semiconductor alloys are a class of materials with applications in the mid and long wave infrared spectrum. The quaternary alloy InAsSbBi is attractive because it can be grown lattice-matched to commercially available GaSb substrates, and the adjustment of the Bi and Sb mole fractions enables both lattice constant and bandgap to be tuned independently. This dissertation provides a comprehensive study of the surface morphology and the structural and chemical properties of InAsSbBi alloys grown by molecular beam epitaxy.
210 nm thick InAsSbBi layers grown at temperatures from 280 °C to 430 °C on (100) on-axis, (100) offcut 1° to (011), and (100) offcut 4° to (111)A GaSb substrates are investigated using Rutherford back scattering, X-ray diffraction, transmission electron microscopy, Nomarski optical microscopy, atomic force microscopy, and photoluminescence spectroscopy. The results indicate that the layers are coherently strained and contain dilute Bi mole fractions.
Large surface droplets with diameters and densities on the order of 3 µm and 106 cm-2 are observed when the growth is performed with As overpressures around 1%. Preferential orientation of the droplets occurs along the [011 ̅] step edges offcut (100) 1° to (011) substrate. The surface droplets are not observed when the As overpressure is increased to 4%. Small crystalline droplets with diameters and densities on the order of 70 nm and 1010 cm-2 are observed between the large droplets for the growth at 430°C. Analysis of one of the small droplets indicates a misoriented zinc blende structure composed of In, Sb, and Bi, with a 6.543 ± 0.038 Å lattice constant.
Lateral variation in the Bi mole fraction is observed in InAsSbBi grown at high temperature (400 °C, 420 °C) on (100) on-axis and (100) offcut 4° to (111)A substrates, but is not observed for growth at 280 °C or on (100) substrates that are offcut 1° to (011). Improved crystal and optical quality is observed in the high temperature grown InAsSbBi and CuPtB type atomic ordering on the {111}B planes is observed in the low temperature grown InAsSbBi. Strain induced tilt is observed in coherently strained InAsSbBi grown on offcut substrates.
210 nm thick InAsSbBi layers grown at temperatures from 280 °C to 430 °C on (100) on-axis, (100) offcut 1° to (011), and (100) offcut 4° to (111)A GaSb substrates are investigated using Rutherford back scattering, X-ray diffraction, transmission electron microscopy, Nomarski optical microscopy, atomic force microscopy, and photoluminescence spectroscopy. The results indicate that the layers are coherently strained and contain dilute Bi mole fractions.
Large surface droplets with diameters and densities on the order of 3 µm and 106 cm-2 are observed when the growth is performed with As overpressures around 1%. Preferential orientation of the droplets occurs along the [011 ̅] step edges offcut (100) 1° to (011) substrate. The surface droplets are not observed when the As overpressure is increased to 4%. Small crystalline droplets with diameters and densities on the order of 70 nm and 1010 cm-2 are observed between the large droplets for the growth at 430°C. Analysis of one of the small droplets indicates a misoriented zinc blende structure composed of In, Sb, and Bi, with a 6.543 ± 0.038 Å lattice constant.
Lateral variation in the Bi mole fraction is observed in InAsSbBi grown at high temperature (400 °C, 420 °C) on (100) on-axis and (100) offcut 4° to (111)A substrates, but is not observed for growth at 280 °C or on (100) substrates that are offcut 1° to (011). Improved crystal and optical quality is observed in the high temperature grown InAsSbBi and CuPtB type atomic ordering on the {111}B planes is observed in the low temperature grown InAsSbBi. Strain induced tilt is observed in coherently strained InAsSbBi grown on offcut substrates.
ContributorsKosireddy, Rajeev Reddy (Author) / Johnson, Shane R (Thesis advisor) / Smith, David J. (Committee member) / Alford, Terry L. (Committee member) / Soignard, Emmanuel (Committee member) / Arizona State University (Publisher)
Created2020
Description
The molecular beam epitaxy growth of the III-V semiconductor alloy indium arsenide antimonide bismide (InAsSbBi) is investigated over a range of growth temperatures and V/III flux ratios. Bulk and quantum well structures grown on gallium antimonide (GaSb) substrates are examined. The relationships between Bi incorporation, surface morphology, growth temperature, and group-V flux are explored. A growth model is developed based on the kinetics of atomic desorption, incorporation, surface accumulation, and droplet formation. The model is applied to InAsSbBi, where the various process are fit to the Bi, Sb, and As mole fractions. The model predicts a Bi incorporation limit for lattice matched InAsSbBi grown on GaSb.The optical performance and bandgap energy of InAsSbBi is examined using photoluminescence spectroscopy. Emission is observed from low to room temperature with peaks ranging from 3.7 to 4.6 μm. The bandgap as function of temperature is determined from the first derivative maxima of the spectra fit to an Einstein single oscillator model. The photoluminescence spectra is observed to significantly broaden with Bi content as a result of lateral composition variations and the highly mismatched nature of Bi atoms, pairs, and clusters in the group-V sublattice.
A bowing model is developed for the bandgap and band offsets of the quinary alloy GaInAsSbBi and its quaternary constituents InAsSbBi and GaAsSbBi. The band anticrossing interaction due to the highly mismatched Bi atoms is incorporated into the relevant bowing terms. An algorithm is developed for the design of mid infrared GaInAsSbBi
quantum wells, with three degrees freedom to independently tune transition energy, in plane strain, and band edge offsets for desired electron and hole confinement.
The physical characteristics of the fundamental absorption edge of the relevant III-V binaries GaAs, GaSb, InAs, and InSb are examined using spectroscopic ellipsometry. A five parameter model is developed that describes the key physical characteristics of the absorption edge, including the bandgap energy, the Urbach tail, and the absorption coefficient at the bandgap.
The quantum efficiency and recombination lifetimes of bulk InAs0.911Sb0.089 grown by molecular beam epitaxy is investigated using excitation and temperature dependent steady state photoluminescence. The Shockley-Read-Hall, radiative, and Auger recombination lifetimes are determined.
A bowing model is developed for the bandgap and band offsets of the quinary alloy GaInAsSbBi and its quaternary constituents InAsSbBi and GaAsSbBi. The band anticrossing interaction due to the highly mismatched Bi atoms is incorporated into the relevant bowing terms. An algorithm is developed for the design of mid infrared GaInAsSbBi
quantum wells, with three degrees freedom to independently tune transition energy, in plane strain, and band edge offsets for desired electron and hole confinement.
The physical characteristics of the fundamental absorption edge of the relevant III-V binaries GaAs, GaSb, InAs, and InSb are examined using spectroscopic ellipsometry. A five parameter model is developed that describes the key physical characteristics of the absorption edge, including the bandgap energy, the Urbach tail, and the absorption coefficient at the bandgap.
The quantum efficiency and recombination lifetimes of bulk InAs0.911Sb0.089 grown by molecular beam epitaxy is investigated using excitation and temperature dependent steady state photoluminescence. The Shockley-Read-Hall, radiative, and Auger recombination lifetimes are determined.
ContributorsSchaefer, Stephen Thomas (Author) / Johnson, Shane R (Thesis advisor) / Zhang, Yong-Hang (Committee member) / Goryll, Michael (Committee member) / King, Richard (Committee member) / Arizona State University (Publisher)
Created2020