The purpose of this thesis is to study the InAs self-organized quantum dots and InAs/GaAsN digital alloys. We have studied the optical properties of these structures after rapid thermal annealing. The measured samples are InGaAs/InAs¡BInGaAs/InAlAs/InAs¡BInGaAs/AlAs/InAs quantum dots and InAs/GaAsN short-period superlattice quantum well structures. We have investigated the effect of different strain-reducing layer (SRL) on the photoluminescence (PL) of self-assembled InAs/GaAs quantum dots. From experiments, the coverage layers of Al composition can increase the energy splitting between the ground and first excited states of the quantum dots. It is related to the thickness and composition of the cap layers. Using thick InAlAs and InGaAs together as a SRL results in the energy splitting up to 123meV. However the PL intensity decreases three times. After rapid thermal annealing up to 800¢XC, the QDs with Al-composed cap layer show no shift of peak wavelength. For InAs/GaAsN digital alloys, through temperature dependent PL spectrum, we can observe PL peak has a blue shift form room temperature to 100K, and a red shift from 100K to 10K. It is similar to the InGaAsN quantum well. However, one of the samples shows temperature insensitive for the PL peaks.

This thesis studies p-i-n GaAs solar cells with self-assembled InAs quantum dots (QDs) inserted. The values of this work lie in three aspects. First, by comparing the cell performance with QDs in the i-region and the n-region, the photocurrent (PC) production from QDs by thermal activation and/or intermediate band (IB) absorption is proved to be much lower in efficiency than tunneling. Second, the efficiency of PC production from QDs, characterized by PC spectrum, is helpful to design QD-based photodetectors. Third, closely spaced InAs QD layers allow a strong inter-layer tunneling, leading to an effective PC production from QD deep states, potential for solar cell application. Fourth, from the temperature-dependent PC spectra the minority photohole thermal escape is found to be dominant on PC production from QDs in the n-region. The thermal activation energy reflects the potential variations formed by electron filling in QDs. Apart from InAs QDs, this thesis also explores the blinking correlation between two colloidal CdSe QDs. For QD distance of 1 µm or less, there is a bunched correlation at delay τ = 0, meaning that the two QDs blink synchronously. Such correlation disappears gradually as QD distance increases. The correlation is possibly caused by the stimulated emission between the two nearby QDs. / QC 20120507

First discovered by Holm and Meissner in 1932, the superconducting proximity effect has remained a subject of experimental and theoretical interest. In recent years, it has been proposed that proximity effect in a semiconductor with large g-factor and spin-orbit coupling could lead to exotic phases of superconductivity. This thesis focuses on proximity effect in one of the prime semiconductor candidates -- InAs nanowires. The first set of experiments investigates the superconducting phase-dependent tunneling spectrum of a proximitized InAs quantum dot. We observe tunneling resonances of Andreev bound states in the Kondo regime, and induce quantum phase transitions of the quantum dot ground state with gate voltage and phase bias -- the latter being the first experimental observation of its kind. An additional zero-bias peak of unknown origin is observed to coexist with the Andreev bounds states. The second set of experiments extends upon the first with sharper tunneling resonances and an increase in the device critical field. By applying an external magnetic field, we observe spin-resolved Andreev bound states in proximitized InAs quantum dots. From the linear splitting of the tunneling resonances, we extract g-factors of 5 and 10 in two different devices. The third set of experiments utilizes a novel type of epitaxial core-shell InAs-Al nanowire. We compare the induced gaps of these nanowires with control devices proximitized with evaporated Al films. Our results show that the epitaxial core-shell nanowires possess a much harder induced gap -- up to two orders of magnitude in sub-gap conductance suppression as compared to a factor of five in evaporated control devices. This observation suggests that roughness in S-N interfaces plays a crucial role in the quality of the proximity effect. The fourth set of experiments investigates the gate-tunability of epitaxial half-shell nanowires. In a half-shell nanowire Josephson junction, we measure the normal state resistance, maximum supercurrent, and magnetic field-dependent supercurrent interference patterns. The gate dependences of these independent experimental parameters are consistent with one another and indicate that an InAs nanowire in good ohmic contact to a thin sliver of Al retains its proximity effect and is gate-tunable. / Physics

InAs/GaSb superlattices are a material system well suited to growth via molecular beam epitaxy. The ability to tune the band gap over the entire mid and long wave infrared spectrum gives a large number of applications for devices made from InAs/GaSb superlattice material. The growth of high quality InAs/GaSb superlattice material requires a careful study of the parameters used during epitaxial growth. This work investigates the growth of tunnel junctions for InAs/GaSb based superlattice light emitting diodes, the presence of defects in GaSb homoepitaxial layers, and variations in the growth rate of InAs/GaSb superlattice samples. Tunnel junctions in cascaded structures must provide adequate barriers to prevent carriers from leaking from one emission region to the next without first recombining radiatively, while at the same time remain low in tunneling resistance for current recycling. A variety of tunnel junction designs are compared in otherwise identical four stage InAs/GaSb superlattice light emitting diodes, which past studies have found hole confinement to be problematic. GaSb was used on the p-side of the junction, while various materials were used on the n-side. Al0.20In0.80As0.73Sb0.27 tunnel junctions function best due to the combination of favorable band alignment and ease of growth. Pyramidal defects have been observed in layers of GaSb grown by molecular beam epitaxy on GaSb substrates. These defects are typically 3-8 nanometers high, 1-3 microns in diameter, and shaped like pyramids. Their occurrence in the growth of GaSb buffer layers can propagate into subsequent layers. Defects are nucleated during the early stages of growth after the thermal desorption of native oxide from the GaSb substrate. These defects grow into pyramids due to a repulsive Ehrlich-Schwoebel potential on atomic step edges leading to an upward adatom current. The defects reduce in density with growth of GaSb. The insertion of a thin AlAsSb layer into the early stages of the GaSb buffer increases the rate of elimination of the defects, resulting in a smooth surface within 500nm. The acceleration of defect reduction is due to the temporary interruption of step-flow growth induced by the AlAsSb layer. This leads to a reduced isolation of the pyramids from the GaSb epitaxial layer, and allows the pyramidal defects to smooth out. Investigations into varying the superlattice growth rate have not been reported widely in the literature. Due to the frequent use of soaks, growth interrupts, and other interface structuring steps the superlattice growth rate and the interface layer sequence are linked. In order to properly study the effects of growth rate variations and interface design changes it is necessary to account for the effect on growth rate due to the interfaces. To this end it is useful to think of the effective growth rate of the superlattice, which is the total layer thickness divided by the total time, per superlattice period. Varying the effective growth rate of superlattice photoluminescence samples shows a peak in output at ˜ 0.5 monolayers per second. Investigations into the structural properties of the superlattices show no decrease in structural uniformity for effective growth rates up to ˜ 1.4 monolayers per second.

THz spinduliuotės generavimas iš puslaidininkių paviršiaus turi didelį potencialą puslaidininkių fizikinėms savybėms tirti. Šis darbas skiriamas puslaidininkių tyrimams generuojant THz impulsus iš jų paviršių, apšviestų femtosekundiniais lazerio impulsais. THz spinduliuotė iš puslaidininkių paviršių gali būti generuojama dėl visos eilės fizikinių mechanizmų: paviršinio lauko ekranavimo, foto-Demberio efekto, optinio lyginimo, elektriniu lauku indukuoto optinio lyginimo, plazminių svyravimų, koherentinių fononų ir plazmonų. Tiriant THz spinduliuotės generacijos mechanizmus galima išmatuoti daug svarbių puslaidininkių parametrų, tokių kaip lūžio rodiklis, judris, krūvininkų gyvavimo trukmė, aukštesniųjų laidumo slėnių padėtys. Darbo metu tirti THz spinduliuotės generacijos puslaidininkio paviršiuje mechanizmai keičiant žadinimo sąlygas: aplinkos temperatūrą, magnetinį lauką, žadinančio lazerio bangos ilgį ir intensyvumą, bei impulso trukmę. Ištyrus visą eilę įvairių puslaidininkių nustatyta, kad geriausias THz spinduliuotės emiteris žadinant 800 nm bangos ilgio spinduliuote yra p-InAs. Pirmą kartą THz žadinimo spektroskopijos metodu tiesiogiai išmatuoti tarpslėniniai atstumai InxGa1-xAs , InAs ir InSb bandiniuose. / Generation of terahertz radiation from semiconductor surfaces has great potential for investigation of physical properties of semiconductors. This work focuses on the semiconductor research when generating terahertz pulses from a variety of semiconductor surfaces. THz radiation from semiconductor surfaces can be generated on a whole range of physical mechanisms: the surface field screening, photo-Dember effect, the optical rectification, electric field induced optical rectification, plasma oscillations, coherent phonons and plasmons. A number of important semiconductor parameters such as refractive index, mobility, carrier relaxation time and higher conductivity valley positions can be measured using THz generation from semiconductor surface technique. In this work THz radiation generation mechanisms were investigated when changing excitation conditions: ambient temperature, magnetic field, laser wavelength and intensity, pulse duration. After tests with variety different semiconductors it was found that p-InAs is the best surface emitter when excitation laser wavelength is 800 nm. Using THz excitation spectroscopy the intervalley distances were measured directly, for the first time, in two InxGa1-xAs, InAs and InSb samples.

Generation of terahertz radiation from semiconductor surfaces has great potential for investigation of physical properties of semiconductors. This work focuses on the semiconductor research when generating terahertz pulses from a variety of semiconductor surfaces. THz radiation from semiconductor surfaces can be generated on a whole range of physical mechanisms: the surface field screening, photo-Dember effect, the optical rectification, electric field induced optical rectification, plasma oscillations, coherent phonons and plasmons. A number of important semiconductor parameters such as refractive index, mobility, carrier relaxation time and higher conductivity valley positions can be measured using THz generation from semiconductor surface technique. In this work THz radiation generation mechanisms were investigated when changing excitation conditions: ambient temperature, magnetic field, laser wavelength and intensity, pulse duration. After tests with variety different semiconductors it was found that p-InAs is the best surface emitter when excitation laser wavelength is 800 nm. Using THz excitation spectroscopy the intervalley distances were measured directly, for the first time, in two InxGa1-xAs, InAs and InSb samples. / THz spinduliuotės generavimas iš puslaidininkių paviršiaus turi didelį potencialą puslaidininkių fizikinėms savybėms tirti. Šis darbas skiriamas puslaidininkių tyrimams generuojant THz impulsus iš jų paviršių, apšviestų femtosekundiniais lazerio impulsais. THz spinduliuotė iš puslaidininkių paviršių gali būti generuojama dėl visos eilės fizikinių mechanizmų: paviršinio lauko ekranavimo, foto-Demberio efekto, optinio lyginimo, elektriniu lauku indukuoto optinio lyginimo, plazminių svyravimų, koherentinių fononų ir plazmonų. Tiriant THz spinduliuotės generacijos mechanizmus galima išmatuoti daug svarbių puslaidininkių parametrų, tokių kaip lūžio rodiklis, judris, krūvininkų gyvavimo trukmė, aukštesniųjų laidumo slėnių padėtys. Darbo metu tirti THz spinduliuotės generacijos puslaidininkio paviršiuje mechanizmai keičiant žadinimo sąlygas: aplinkos temperatūrą, magnetinį lauką, žadinančio lazerio bangos ilgį ir intensyvumą, bei impulso trukmę. Ištyrus visą eilę įvairių puslaidininkių nustatyta, kad geriausias THz spinduliuotės emiteris žadinant 800 nm bangos ilgio spinduliuote yra p-InAs. Pirmą kartą THz žadinimo spektroskopijos metodu tiesiogiai išmatuoti tarpslėniniai atstumai InxGa1-xAs , InAs ir InSb bandiniuose.

Spin-dependent phenomena in semiconductor nanowires have recently gained a lot of attention, in special because these nanostructures can be a viable setup to study exotic states of matter like the Majorana fermions. One of the key ingredients to accommodate the Majorana zero modes is the spin-orbit coupling in the nanowires, which has been usually treated with two-band Hamiltonians. The spin-orbit coupling in semiconductors arise from two distinct sources being the bulk inversion asymmetry, when the unit cell does not present inversion symmetry, e.g. when the crystal unit cell is composed by two different atoms, and the structural inversion asymmetry, when the whole system does not have a mirror symmetry. To describe the system these effective models take as input, parameters that are dependent on the system configuration and measurement setups. Although these effective models have been successful in determine relevant physical properties, a more realistic description of the interacting energy bands is required, specially in quantum confined systems where the interplay between both sources of spin-orbit coupling can change the systems properties in non-trivial ways. For instance, in quantum wells there is an anisotropy of the g-factor due to the quantum confinement and structural inversion asymmetry. Furthermore, the in-plane g-factor also have an anisotropy which is due to the intrinsic spin-orbit coupling and it is not captured by these effective models. In this study, we use realistic multiband k · p Hamiltonians, including both spin-orbit coupling mechanisms, to determine the band structure of zincblende InSb and wurtzite InAs nanowires under a transverse electric field. We analyze the effects of the lateral quantum confinement for a hexagonal cross-section geometry and of the change in growth directions, extracting the relevant physical parameters for the first conduction subband. We found that the g-factors are heavily dependent on the quantum confinement and nanowire orientation, with in-plane/out-of-plane anisotropies up to 3%. We also found that for zinc-blende nanowires the extrinsic spin-orbit coupling is dominant over the intrinsic one whereas, for wurztize, the opposite behavior holds. In order to assess if the nanowires could host the aforementioned Majorana zero modes we investigate under which circumstances the topological phase transition occurs, using the Bogoliubov-de Gennes formalism to couple the nanowire with a superconductor, and we found that using realistic and experimental feasible parameters, indeed, the phase transition occurs. In conclusion, our systematic investigation of nanowires shows that the spin-orbit coupling energy can be fine tuned by the external electric field in experimentally achievable setups that ultimately could guide the search for the elusive Majorana modes. Moreover, our numerical approach is not restricted to a specific material or dimensionality and can be used to study others systems to provide useful insights into the electronic and spintronic fields. / Recentemente, fenômenos dependentes de spin em nanofios semicondutores se tornaram uma área de pesquisa ativa especialmente porque essas nanoestruturas podem ser viáveis para o estudo de estados exóticos da matéria como, por exemplo, os férmions de Majorana. Um dos ingredientes chave para que esses modos de excitação possam existir em nanofios é o acoplamento spin-órbita, o qual tem sido usualmente tratado com modelos de duas bandas. O acoplamento spin-órbita em semicondutores aparece de duas fontes distintas sendo elas a assimetria de inversão no bulk, quando a célula unitária do cristal não possui simetria de inversão, por exemplo, quando é formada por dois átomos diferentes, e a assimetria de inversão estrutural, quando o sistema como um todo não possui simetria de inversão. Para descrever o sistema, os modelos efetivos de duas bandas usam como entrada parâmetros que dependem tanto do sistema específico quanto da configuração do arranjo experimental. Apesar desses modelos terem sucesso em descrever algumas das propriedades físicas relevantes, uma descrição mais realística da interação entre as bandas de energia se faz necessária, especialmente em sistemas com confinamento quântico onde a ação combinada das duas fontes de acoplamento spin-órbita muda as propriedades do sistema de maneira não-trivial. Por exemplo, o fator giromagnético em poços quânticos é anisotrópico devido aos efeitos de ambos, confinamento quântico e a assimetria de inversão estrutural. Ademais, o fator giromagnético ao longo do plano também possui uma anisotropia, a qual tem origem no acoplamento spin-órbita intrínseco do sistema e não é capturada por esses modelos efetivos. Nesse estudo, nós usamos Hamiltonianos k · p multibanda, incluindo ambos os mecanismos de acoplamento spin-órbita, para determinar a estrutura de bandas de nanofios de InSb na fase blenda de zinco e InAs na fase wurtzita sob a ação de um campo elétrico transversal. Nós analisamos os efeitos do confinamento quântico lateral, para fios com seção transversal hexagonal, e diferentes direções de crescimento, extraindo parâmetros físicos relevantes para a primeira sub-banda de condução. Nós encontramos que os fatores giromagnéticos são fortemente influenciados pelo confinamento quântico e orientação dos nanofios, com anisotropias no plano e fora do plano de até 3%. Nós também encontramos que para nanofios de InSb na fase blenda de zinco, o acoplamento spin-órbita extrínseco domina o intrínseco enquanto que, em nanofios de InAs na fase wurtzita, vale o oposto. Para avaliar se os nanofios podem hospedar os modos de Majorana de energia zero nós investigamos sob quais circunstâncias a transição de fase topológica ocorre usando o formalismo de Bogoliubov-de Gennes para acoplar o nanofio a um supercondutor, e encontramos que usando nossos parâmetros e em condições experimentalmente factíveis, de fato, a transição de fase ocorre. Em conclusão, nossa investigação sistemática nos nanofios mostrou que o acoplamento spin-órbita pode ser ajustado por fontes externas, tais como um campo elétrico aplicado, e em configurações experimentais factíveis e que ultimamente pode guiar à busca dos elusivos modos de Majorana. Além do mais, nossa abordagem numérica não é restrita a esses materiais em específico e nem a nanofios, podendo ser usada para estudar outros sistemas provendo intuições úteis nos campos de eletrônica e spintrônica.

Application of InAs/AlSb materials system for development of short-wavelength quantum cascade lasers is explored. Molecular beam epitaxy (MBE) technology allowing to grow multiperiodical unstrained InAs/AlSb heterostructures with roughness of 1-2 monolayers is developed. It is demonstrated that InAs/AlSb materials system is well-suitable for development of short-wavelength quantum cascade lasers operating below 4 µm wavelength. Lasers containing plasmon-enhanced waveguides as well as the short period InAs/AlSb superlattices as waveguides were designed, MBE-grown and studied. The effect of waveguide properties on the device parameters is revealed. Usage of these waveguides and innovations in laser active region introducing “funnel” injector allowed one to reach operation temperature 420 K at the emission wavelength of 3.3 µm. The obtained optical peak power exceeded 1 W per facet. The room temperature operation has been obtained at wavelength below 3 µm. As for wavelength range, applying the new active region design strategy and the short period InAs/AlSb superlattice spacers InAs based quantum cascade lasers emitting at the wavelengths as short as 2.63 µm were developed, which is today the shortest emission wavelength of the operation of semiconductor lasers based on the intersubband transitions. / Disertaciniame darbe nagrinėjamas InAs/AlSb medžiagų sistemos panaudojimas trumpabangių tarppajuostinių lazerių kūrimui. Buvo išplėtota molekulinių pluoštelių epitaksijos technologija, leidžianti auginti daugiaperiodines neįtemptas InAs/AlSb heterosandūras su mažu 1-2 atominių sluoksnių šiurkštumu. Buvo parodyta, jog InAs/AlSb medžiagų sistema yra tinkama kurti trumpabangiams kvantiniams kaskadiniams lazeriams, veikiantiems žemiau 4 µm bangos ilgio ribos. Buvo ištirtas kvantinių kaskadinių lazerių, turinčių tiek plazmoninius bangolaidžius su stipriai legiruotais InAs apdariniais sluoksniais, tiek ir mažo periodo InAs/AlSb supergardelių bangolaidžius, veikimas bei jų įtaka prietaiso parametrams. Šie sprendimai dėl bangolaidžių bei tolimesni aktyviosios terpės patobulinimai, naudojant piltuvėlio formos injektorių, leido sukurti didelio našumo prietaisus, galinčius veikti iki 420 K temperatūros, esant 3,3 µm bangos ilgio emisijai, ir pasiekti maksimalią optinę galią siekiančią 1 W kambario temperatūroje. Šios inovacijos leido sukurti ir InAs/AlSb kvantinį kaskadinį lazerį, emituojantį ~2,6 µm bangos ilgio spinduliuotę  šiai dienai tai yra trumpiausią bangos ilgį spinduliuojantis tokio tipo prietaisas pasaulyje.

Disertaciniame darbe nagrinėjamas InAs/AlSb medžiagų sistemos panaudojimas trumpabangių tarppajuostinių lazerių kūrimui. Buvo išplėtota molekulinių pluoštelių epitaksijos technologija, leidžianti auginti daugiaperiodines neįtemptas InAs/AlSb heterosandūras su mažu 1-2 atominių sluoksnių šiurkštumu. Buvo parodyta, jog InAs/AlSb medžiagų sistema yra tinkama kurti trumpabangiams kvantiniams kaskadiniams lazeriams, veikiantiems žemiau 4 µm bangos ilgio ribos. Buvo ištirtas kvantinių kaskadinių lazerių, turinčių tiek plazmoninius bangolaidžius su stipriai legiruotais InAs apdariniais sluoksniais, tiek ir mažo periodo InAs/AlSb supergardelių bangolaidžius, veikimas bei jų įtaka prietaiso parametrams. Šie sprendimai dėl bangolaidžių bei tolimesni aktyviosios terpės patobulinimai, naudojant piltuvėlio formos injektorių, leido sukurti didelio našumo prietaisus, galinčius veikti iki 420 K temperatūros, esant 3,3 µm bangos ilgio emisijai, ir pasiekti maksimalią optinę galią siekiančią 1 W kambario temperatūroje. Šios inovacijos leido sukurti ir InAs/AlSb kvantinį kaskadinį lazerį, emituojantį ~2,6 µm bangos ilgio spinduliuotę  šiai dienai tai yra trumpiausią bangos ilgį spinduliuojantis tokio tipo prietaisas pasaulyje. / Application of InAs/AlSb materials system for development of short-wavelength quantum cascade lasers is explored. Molecular beam epitaxy (MBE) technology allowing to grow multiperiodical unstrained InAs/AlSb heterostructures with roughness of 1-2 monolayers is developed. It is demonstrated that InAs/AlSb materials system is well-suitable for development of short-wavelength quantum cascade lasers operating below 4 µm wavelength. Lasers containing plasmon-enhanced waveguides as well as the short period InAs/AlSb superlattices as waveguides were designed, MBE-grown and studied. The effect of waveguide properties on the device parameters is revealed. Usage of these waveguides and innovations in laser active region introducing “funnel” injector allowed one to reach operation temperature 420 K at the emission wavelength of 3.3 µm. The obtained optical peak power exceeded 1 W per facet. The room temperature operation has been obtained at wavelength below 3 µm. As for wavelength range, applying the new active region design strategy and the short period InAs/AlSb superlattice spacers InAs based quantum cascade lasers emitting at the wavelengths as short as 2.63 µm were developed, which is today the shortest emission wavelength of the operation of semiconductor lasers based on the intersubband transitions.

Spin-dependent phenomena in semiconductor nanowires have recently gained a lot of attention, in special because these nanostructures can be a viable setup to study exotic states of matter like the Majorana fermions. One of the key ingredients to accommodate the Majorana zero modes is the spin-orbit coupling in the nanowires, which has been usually treated with two-band Hamiltonians. The spin-orbit coupling in semiconductors arise from two distinct sources being the bulk inversion asymmetry, when the unit cell does not present inversion symmetry, e.g. when the crystal unit cell is composed by two different atoms, and the structural inversion asymmetry, when the whole system does not have a mirror symmetry. To describe the system these effective models take as input, parameters that are dependent on the system configuration and measurement setups. Although these effective models have been successful in determine relevant physical properties, a more realistic description of the interacting energy bands is required, specially in quantum confined systems where the interplay between both sources of spin-orbit coupling can change the systems properties in non-trivial ways. For instance, in quantum wells there is an anisotropy of the g-factor due to the quantum confinement and structural inversion asymmetry. Furthermore, the in-plane g-factor also have an anisotropy which is due to the intrinsic spin-orbit coupling and it is not captured by these effective models. In this study, we use realistic multiband k · p Hamiltonians, including both spin-orbit coupling mechanisms, to determine the band structure of zincblende InSb and wurtzite InAs nanowires under a transverse electric field. We analyze the effects of the lateral quantum confinement for a hexagonal cross-section geometry and of the change in growth directions, extracting the relevant physical parameters for the first conduction subband. We found that the g-factors are heavily dependent on the quantum confinement and nanowire orientation, with in-plane/out-of-plane anisotropies up to 3%. We also found that for zinc-blende nanowires the extrinsic spin-orbit coupling is dominant over the intrinsic one whereas, for wurztize, the opposite behavior holds. In order to assess if the nanowires could host the aforementioned Majorana zero modes we investigate under which circumstances the topological phase transition occurs, using the Bogoliubov-de Gennes formalism to couple the nanowire with a superconductor, and we found that using realistic and experimental feasible parameters, indeed, the phase transition occurs. In conclusion, our systematic investigation of nanowires shows that the spin-orbit coupling energy can be fine tuned by the external electric field in experimentally achievable setups that ultimately could guide the search for the elusive Majorana modes. Moreover, our numerical approach is not restricted to a specific material or dimensionality and can be used to study others systems to provide useful insights into the electronic and spintronic fields. / Recentemente, fenômenos dependentes de spin em nanofios semicondutores se tornaram uma área de pesquisa ativa especialmente porque essas nanoestruturas podem ser viáveis para o estudo de estados exóticos da matéria como, por exemplo, os férmions de Majorana. Um dos ingredientes chave para que esses modos de excitação possam existir em nanofios é o acoplamento spin-órbita, o qual tem sido usualmente tratado com modelos de duas bandas. O acoplamento spin-órbita em semicondutores aparece de duas fontes distintas sendo elas a assimetria de inversão no bulk, quando a célula unitária do cristal não possui simetria de inversão, por exemplo, quando é formada por dois átomos diferentes, e a assimetria de inversão estrutural, quando o sistema como um todo não possui simetria de inversão. Para descrever o sistema, os modelos efetivos de duas bandas usam como entrada parâmetros que dependem tanto do sistema específico quanto da configuração do arranjo experimental. Apesar desses modelos terem sucesso em descrever algumas das propriedades físicas relevantes, uma descrição mais realística da interação entre as bandas de energia se faz necessária, especialmente em sistemas com confinamento quântico onde a ação combinada das duas fontes de acoplamento spin-órbita muda as propriedades do sistema de maneira não-trivial. Por exemplo, o fator giromagnético em poços quânticos é anisotrópico devido aos efeitos de ambos, confinamento quântico e a assimetria de inversão estrutural. Ademais, o fator giromagnético ao longo do plano também possui uma anisotropia, a qual tem origem no acoplamento spin-órbita intrínseco do sistema e não é capturada por esses modelos efetivos. Nesse estudo, nós usamos Hamiltonianos k · p multibanda, incluindo ambos os mecanismos de acoplamento spin-órbita, para determinar a estrutura de bandas de nanofios de InSb na fase blenda de zinco e InAs na fase wurtzita sob a ação de um campo elétrico transversal. Nós analisamos os efeitos do confinamento quântico lateral, para fios com seção transversal hexagonal, e diferentes direções de crescimento, extraindo parâmetros físicos relevantes para a primeira sub-banda de condução. Nós encontramos que os fatores giromagnéticos são fortemente influenciados pelo confinamento quântico e orientação dos nanofios, com anisotropias no plano e fora do plano de até 3%. Nós também encontramos que para nanofios de InSb na fase blenda de zinco, o acoplamento spin-órbita extrínseco domina o intrínseco enquanto que, em nanofios de InAs na fase wurtzita, vale o oposto. Para avaliar se os nanofios podem hospedar os modos de Majorana de energia zero nós investigamos sob quais circunstâncias a transição de fase topológica ocorre usando o formalismo de Bogoliubov-de Gennes para acoplar o nanofio a um supercondutor, e encontramos que usando nossos parâmetros e em condições experimentalmente factíveis, de fato, a transição de fase ocorre. Em conclusão, nossa investigação sistemática nos nanofios mostrou que o acoplamento spin-órbita pode ser ajustado por fontes externas, tais como um campo elétrico aplicado, e em configurações experimentais factíveis e que ultimamente pode guiar à busca dos elusivos modos de Majorana. Além do mais, nossa abordagem numérica não é restrita a esses materiais em específico e nem a nanofios, podendo ser usada para estudar outros sistemas provendo intuições úteis nos campos de eletrônica e spintrônica.