Spintronic semiconductor devices based on Mn doped GaAs

Natalia Lebedeva

Spintronic semiconductor devices based on Mn doped GaAs

Julkaisun otsikon käännös: Mangaanilla seostetuista GaAs-ohutkalvoista valmistetut spintroniikan puolijohdekomponentit

Natalia Lebedeva

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Työssä tutkittiin teoreettisesti ja kokeellisesti voimakkaan vaihtovuorovaikutuksen, magneettisen järjestäytymisen, ja spin-fluktuaatioiden vaikutuksia spintroniikan puolijohdekomponenttien sähköisiin kuljetusominaisuuksiin. Oleellisena osana tutkittujen komponettien rakennetta oli magnaanilla seostettu GaAs-kerros tai ferromagneettinen kvanttipiste. Tutkittuja komponentteja olivat pn-liitokset, Schottky-diodit, spin Esaki-Zener- tunnelidiodit, resonanssitunnelidiodit, ja ferromagneettiseen kvantti-pisteeseen perustuvat yksielektroni-transistorit. Komponenttien mallinnuksessa käytettiin Greenin funktiotekniikkaa, kuten Keldyshin Greenin funktioita, mikä mahdollisti tarkan kvanttistatistisen mallinnuksen, jossa otettiin huomioon mm. sironnan vaikutus kvanttimekaanisesti laskettujen energiatilojen leviämiseen. Mallit ennustivat voimakkaasti varauksenkuljettajien spinistä riippuvia kuljetusilmiöitä, kuten magnetoresistanssia ja spinistä riippuvaa tunneloitumista, erityisesti ferromagneettisen transitiopisteen läheisyydessä ja ulkoisen magneettikentän vaikuttaessa. Malli ferromagneettisille kvanttipisteille ennusti Kondo-tyyppistä konduktanssiresonanssia korkeissa lämpötiloissa. Työn kokeellisessa osassa valmistettiin useita spintroniikan puolijohdekomponentteja kuten ferromagnettisia diodeja käyttäen Molekyylisuihku-tekniikkaa mangaanilla seostettujen GaAs-ohutkalvojen kasvatuksessa. Komponenttien sähköisiä ja magneettisia ominaisuuksia tutkittiin mittaamalla I-V ominaiskäyrät, Hall ilmiö, magnetoresistanssi ja magnetointi lämpötilan ja magneettikentän funktiona. Tärkein tulos oli epäisotrooppisen tunnelimagnetoresistanssi-ilmiön löytyminen Esaki-Zener-tunnelidiodeissa ja ferromagneettisissa resonanssitunnelidiodeissa. Ilmiö havaittiin myös hyvin pienillä jännitteillä, mikä periaatteessa mahdollistaa hyvin pienitehoisten spintroniikan komponenttien toteutuksen. Työssä kehitetyt teoreettiset mallit selittivät havaitut magnetosähköiset ilmiöt. Esimerkiksi spin-epäjärjestyssironnan malli kuvasi tarkasti Mn-seostetuissa GaAs-ohutkalvoissa mitatun resistiivisyyden ja magnetoresistanssin laajalla lämpötila-alueella ja kaikilla mittauksissa käytetyillä magneettikenttäarvoilla.

Julkaisun otsikon käännös	Mangaanilla seostetuista GaAs-ohutkalvoista valmistetut spintroniikan puolijohdekomponentit
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Kuivalainen, Pekka, Vastuuprofessori Novikov, Sergey, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-5389-9
Sähköinen ISBN	978-952-60-5390-5
Tila	Julkaistu - 2013
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

spintroniikka
galliumarsenidi
puolijohdeteknologia
magnetoresistanssi
tunnelointi-ilmiöt

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-5390-5

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@phdthesis{1d185168c50e47c69eacc84b4a18fb16,

title = "Spintronic semiconductor devices based on Mn doped GaAs",

abstract = "The effects of the strong sp-d exchange interaction, ferromagnetic ordering and large spin fluctuations on the electrical transport properties of various spintronic semiconductor devices have been studied both theoretically and experimentally. The studied devices, which either have a ferromagnetic Mn doped GaAs layer or a Mn doped quantum dot as a central part of the device structure, included pn- and Schottky diodes, Esaki-Zener tunnel diodes, resonant tunnelling diodes, and ferromagnetic single electron transistors consisting of ferromagnetic quantum dots. The modeling of the spintronic devices utilized the advanced Green's function techniques, such as Keldysh Green's functions, which allowed accurate modeling by combining the quantum mechanically calculated electronic structure of the devices with the quantum statistical transport theory. This way the effects of scattering and collisional broadening of the energy levels could also be conveniently included in the models. The models predicted strongly spin-dependent transport and large changes in the magnetotransport properties of the spintronic semiconductor devices at temperatures close to the ferromagnetic ordering temperature or in moderate magnetic fields. The model for the ferromagnetic quantum dots predicted Kondo-like resonances in the conductance at high temperatures. In the experimental part of the work the ferromagnetic thin films, pn-junctions, Esaki-Zener tunnel diodes, Schottky diodes, and resonant tunnelling diodes were fabricated using Molecular Beam Epitaxy technique for the growth of the Mn doped GaAs layers. The electrical and magnetic properties of these devices were studied by measuring the I-V characteristics, Hall effect, magnetoresistance, and magnetization as a function of temperature and magnetic field. The main result was the observation of the tunnelling anisotropic magnetoresistance effect (TAMR) in the Esaki-Zener tunnel diodes and the resonant tunnelling diodes. The effect was observed at very low bias voltages, which might allow the realization of ultra low-power spintronic devices. The developed models explained the measured magnetotransport properties. As an example, applying the spin-disorder scattering model a good quantitative agreement was obtained between the measured and calculated resistance and magnetoresistance in Mn doped GaAs layers in wide temperature and magnetic field ranges.",

keywords = "spintronics, gallium arsenide, semiconductor technology, magnetotransport, tunnelling effects, spintroniikka, galliumarsenidi, puolijohdeteknologia, magnetoresistanssi, tunnelointi-ilmi{\"o}t, spintronics, gallium arsenide, semiconductor technology, magnetotransport, tunnelling effects",

author = "Natalia Lebedeva",

year = "2013",

language = "English",

isbn = "978-952-60-5389-9",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "168",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Spintronic semiconductor devices based on Mn doped GaAs

AU - Lebedeva, Natalia

PY - 2013

Y1 - 2013

N2 - The effects of the strong sp-d exchange interaction, ferromagnetic ordering and large spin fluctuations on the electrical transport properties of various spintronic semiconductor devices have been studied both theoretically and experimentally. The studied devices, which either have a ferromagnetic Mn doped GaAs layer or a Mn doped quantum dot as a central part of the device structure, included pn- and Schottky diodes, Esaki-Zener tunnel diodes, resonant tunnelling diodes, and ferromagnetic single electron transistors consisting of ferromagnetic quantum dots. The modeling of the spintronic devices utilized the advanced Green's function techniques, such as Keldysh Green's functions, which allowed accurate modeling by combining the quantum mechanically calculated electronic structure of the devices with the quantum statistical transport theory. This way the effects of scattering and collisional broadening of the energy levels could also be conveniently included in the models. The models predicted strongly spin-dependent transport and large changes in the magnetotransport properties of the spintronic semiconductor devices at temperatures close to the ferromagnetic ordering temperature or in moderate magnetic fields. The model for the ferromagnetic quantum dots predicted Kondo-like resonances in the conductance at high temperatures. In the experimental part of the work the ferromagnetic thin films, pn-junctions, Esaki-Zener tunnel diodes, Schottky diodes, and resonant tunnelling diodes were fabricated using Molecular Beam Epitaxy technique for the growth of the Mn doped GaAs layers. The electrical and magnetic properties of these devices were studied by measuring the I-V characteristics, Hall effect, magnetoresistance, and magnetization as a function of temperature and magnetic field. The main result was the observation of the tunnelling anisotropic magnetoresistance effect (TAMR) in the Esaki-Zener tunnel diodes and the resonant tunnelling diodes. The effect was observed at very low bias voltages, which might allow the realization of ultra low-power spintronic devices. The developed models explained the measured magnetotransport properties. As an example, applying the spin-disorder scattering model a good quantitative agreement was obtained between the measured and calculated resistance and magnetoresistance in Mn doped GaAs layers in wide temperature and magnetic field ranges.

AB - The effects of the strong sp-d exchange interaction, ferromagnetic ordering and large spin fluctuations on the electrical transport properties of various spintronic semiconductor devices have been studied both theoretically and experimentally. The studied devices, which either have a ferromagnetic Mn doped GaAs layer or a Mn doped quantum dot as a central part of the device structure, included pn- and Schottky diodes, Esaki-Zener tunnel diodes, resonant tunnelling diodes, and ferromagnetic single electron transistors consisting of ferromagnetic quantum dots. The modeling of the spintronic devices utilized the advanced Green's function techniques, such as Keldysh Green's functions, which allowed accurate modeling by combining the quantum mechanically calculated electronic structure of the devices with the quantum statistical transport theory. This way the effects of scattering and collisional broadening of the energy levels could also be conveniently included in the models. The models predicted strongly spin-dependent transport and large changes in the magnetotransport properties of the spintronic semiconductor devices at temperatures close to the ferromagnetic ordering temperature or in moderate magnetic fields. The model for the ferromagnetic quantum dots predicted Kondo-like resonances in the conductance at high temperatures. In the experimental part of the work the ferromagnetic thin films, pn-junctions, Esaki-Zener tunnel diodes, Schottky diodes, and resonant tunnelling diodes were fabricated using Molecular Beam Epitaxy technique for the growth of the Mn doped GaAs layers. The electrical and magnetic properties of these devices were studied by measuring the I-V characteristics, Hall effect, magnetoresistance, and magnetization as a function of temperature and magnetic field. The main result was the observation of the tunnelling anisotropic magnetoresistance effect (TAMR) in the Esaki-Zener tunnel diodes and the resonant tunnelling diodes. The effect was observed at very low bias voltages, which might allow the realization of ultra low-power spintronic devices. The developed models explained the measured magnetotransport properties. As an example, applying the spin-disorder scattering model a good quantitative agreement was obtained between the measured and calculated resistance and magnetoresistance in Mn doped GaAs layers in wide temperature and magnetic field ranges.

KW - spintronics

KW - gallium arsenide

KW - semiconductor technology

KW - magnetotransport

KW - tunnelling effects

KW - spintroniikka

KW - galliumarsenidi

KW - puolijohdeteknologia

KW - magnetoresistanssi

KW - tunnelointi-ilmiöt

KW - spintronics

KW - gallium arsenide

KW - semiconductor technology

KW - magnetotransport

KW - tunnelling effects

M3 - Doctoral Thesis

SN - 978-952-60-5389-9

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Spintronic semiconductor devices based on Mn doped GaAs

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