Synchrotron radiation x-ray topography of crystallographic defects in GaN

Sakari Sintonen

Synchrotron radiation x-ray topography of crystallographic defects in GaN

Julkaisun otsikon käännös: GaN:in kidevirheiden synkrotronisäteilyröntgentopografia

Sakari Sintonen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Tässä työssä tutkittiin galliumnitridi (GaN) -substraattien, sekä hetero- että homoepitaktisten GaN-kerrosten kiderakenteita synkrotronisäteilyröntgentopografian (SR-XRT), röntgendiffraktion (XRD) ja selektiivisen kidevirhesyövytyksen (DSE) avulla. Työssä määritettiin ruuvi- ja sekadislokaatioiden topografiakuviin aiheuttamat kontrastimuutokset. Ruuvidislokaatioiden ja ruuvidislokaatiokertymien jännityskenttien vaikutus topografiakuviin määritettiin simuloimalla, ja simuloidut sekä kokeelliset ammonotermisestä GaN-alustasta tallennetut kuvat vastasivat toisiaan erinomaisesti. Tutkimuksessa havaittiin myös topografiakuvia jännityskentistä, jotka vastasivat suuria dislokaatioita, joiden Burgersin vektorit ovat alkeisruuvidislokaation Burgersin vektorin monikertoja. Kyseiset topografiakuvat voivat olla seurausta joko yksittäisistä suurista dislokaatioista, eli superruuvidislokaatioista tai mikroputkista, tai lähekkäin olevien alkeisruuvidislokaatioiden kokoelmasta. DSE-kokeiden avulla havaittiin, että kaikissa, paitsi yhdessä tapauksessa, kyseessä oli useamman dislokaation yhteenlasketun jänityskentän aiheuttamasta topografiakuvasta. Seka- ja ruuvidislokaatioiden määritettyjä topografiaulkoasuja hyödynnettiin ammonotermisesti kasvatettujen kiteiden laajan alueen kidevirheanalyyissä. Havaittiin, että yhdessä näytteessä sekadislokaatiot muodostivat identtisten Burgersin vektorien dislokaatiojonoja. Kidevirhejonojen aiheuttamat pienet hilakallistukset ja hilapyöritykset laskettiin dislokaatioiden etäisyyksien avulla, ja tulokset todennettiin hyödyntäen korkean resoluution XRD-mittauksia. Työssä analysoitiin myös SR-XRT mittauksien avulla raerajoja ja pohjatason kidevirheitä. Homoepitaktisten ja heteroepitaktisten GaN-kerrosten kidelaatua tutkittiin SR-XRT:n ja XRD:n avulla. GaN-kerrokset valmistettiin metallo-organic vapour phase epitaxy (MOVPE) -menetelmää käyttäen ammonotermisten GaN-alustojen, kuvioitujen safiirialustojen ja kuvioitujen GaN/safiiri-alustojen päälle. GaN/safiirialustat valmistettiin kuvioimalla safiirin päälle kasvatettuja MOVPE GaN-kerroksia. SR-XRT on erityisen sopiva menetelmä matalan kidevirhetiheyden materiaalin tutkimiseen. XRD puolestaan soveltuu hyvin myös korkeamman kidevirhetiheyden materiaalien karakterisointiin. SR-XRT mittaukset mahdollistivat yksittäisten dislokaatioiden kuvantamisen sekä dislokaatiotyyppien määrittämisen.

Julkaisun otsikon käännös	GaN:in kidevirheiden synkrotronisäteilyröntgentopografia
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Lipsanen, Harri, Vastuuprofessori Suihkonen, Sami, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-5969-3
Sähköinen ISBN	978-952-60-5970-9
Tila	Julkaistu - 2014
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

galliumnitridi
dislokaatiot
topografia
röntgendiffraktio

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-5970-9

Siteeraa tätä

@phdthesis{f2e5387906544d0cbd01879b4984b880,

title = "Synchrotron radiation x-ray topography of crystallographic defects in GaN",

abstract = "In this thesis, the crystal structures of bulk, homoepitaxial and heteroepitaxial GaN were characterized by synchrotron radiation x-ray topography (SR-XRT), x-ray diffraction (XRD) and defect selective etching (DSE). The SR-XRT image contrast of threading screw dislocations and threading mixed dislocations in GaN were determined. The images caused by the strain fields of threading screw dislocations and threading screw dislocation clusters were simulated, and the simulated and experimental topograph images of low defect density ammonothermal GaN were in excellent agreement. Topograph images corresponding to strain fields of large dislocations with Burgers vector magnitudes equal to multiples of the elemental screw dislocation Burgers vector were observed. DSE experiments were performed to determine whether these large defect images originate from single dislocation strain fields, i.e. super screw dislocations or micropipes, or from combined strain fields of several elemental dislocations in close proximity. DSE images revealed that all observations but one were caused by groups of adjacent elemental threading dislocations. The determined topograph image contrasts of threading mixed and threading screw dislocations were utilized in large area studies of bulk GaN grown by the ammonothermal method. In one of the studies, threading mixed dislocations were observed to form arrays consisting of mixed dislocations with identical Burgers vectors. The minute lattice tilt and twist caused by the dislocation arrays were calculated based on dislocation spacing and confirmed with high resolution XRD measurements. SR-XRT analysis of grain boundaries and basal plane dislocations in ammonothermal GaN were also discussed. The structural quality of homoepitaxial GaN and heteroepitaxial GaN on patterned substrates was characterized by SR-XRT and XRD. The GaN layers were grown by metallo-organic vapour phase epitaxy (MOVPE) on ammonothermal GaN substrates, patterned sapphire substrates and substrates consisting of patterned MOVPE grown GaN layers on sapphire. SR-XRT is a technique especially suited for imaging the defect structure of materials with low crystalline defect density, whereas XRD is applicable to characterization of materials with higher defect density as well. SR-XRT measurements enabled imaging of individual dislocations and identification of different dislocation types.",

keywords = "gallium nitride, dislocations, topography, x-ray diffraction, galliumnitridi, dislokaatiot, topografia, r{\"o}ntgendiffraktio, gallium nitride, dislocations, topography, x-ray diffraction",

author = "Sakari Sintonen",

year = "2014",

language = "English",

isbn = "978-952-60-5969-3",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "187",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Synchrotron radiation x-ray topography of crystallographic defects in GaN

AU - Sintonen, Sakari

PY - 2014

Y1 - 2014

N2 - In this thesis, the crystal structures of bulk, homoepitaxial and heteroepitaxial GaN were characterized by synchrotron radiation x-ray topography (SR-XRT), x-ray diffraction (XRD) and defect selective etching (DSE). The SR-XRT image contrast of threading screw dislocations and threading mixed dislocations in GaN were determined. The images caused by the strain fields of threading screw dislocations and threading screw dislocation clusters were simulated, and the simulated and experimental topograph images of low defect density ammonothermal GaN were in excellent agreement. Topograph images corresponding to strain fields of large dislocations with Burgers vector magnitudes equal to multiples of the elemental screw dislocation Burgers vector were observed. DSE experiments were performed to determine whether these large defect images originate from single dislocation strain fields, i.e. super screw dislocations or micropipes, or from combined strain fields of several elemental dislocations in close proximity. DSE images revealed that all observations but one were caused by groups of adjacent elemental threading dislocations. The determined topograph image contrasts of threading mixed and threading screw dislocations were utilized in large area studies of bulk GaN grown by the ammonothermal method. In one of the studies, threading mixed dislocations were observed to form arrays consisting of mixed dislocations with identical Burgers vectors. The minute lattice tilt and twist caused by the dislocation arrays were calculated based on dislocation spacing and confirmed with high resolution XRD measurements. SR-XRT analysis of grain boundaries and basal plane dislocations in ammonothermal GaN were also discussed. The structural quality of homoepitaxial GaN and heteroepitaxial GaN on patterned substrates was characterized by SR-XRT and XRD. The GaN layers were grown by metallo-organic vapour phase epitaxy (MOVPE) on ammonothermal GaN substrates, patterned sapphire substrates and substrates consisting of patterned MOVPE grown GaN layers on sapphire. SR-XRT is a technique especially suited for imaging the defect structure of materials with low crystalline defect density, whereas XRD is applicable to characterization of materials with higher defect density as well. SR-XRT measurements enabled imaging of individual dislocations and identification of different dislocation types.

AB - In this thesis, the crystal structures of bulk, homoepitaxial and heteroepitaxial GaN were characterized by synchrotron radiation x-ray topography (SR-XRT), x-ray diffraction (XRD) and defect selective etching (DSE). The SR-XRT image contrast of threading screw dislocations and threading mixed dislocations in GaN were determined. The images caused by the strain fields of threading screw dislocations and threading screw dislocation clusters were simulated, and the simulated and experimental topograph images of low defect density ammonothermal GaN were in excellent agreement. Topograph images corresponding to strain fields of large dislocations with Burgers vector magnitudes equal to multiples of the elemental screw dislocation Burgers vector were observed. DSE experiments were performed to determine whether these large defect images originate from single dislocation strain fields, i.e. super screw dislocations or micropipes, or from combined strain fields of several elemental dislocations in close proximity. DSE images revealed that all observations but one were caused by groups of adjacent elemental threading dislocations. The determined topograph image contrasts of threading mixed and threading screw dislocations were utilized in large area studies of bulk GaN grown by the ammonothermal method. In one of the studies, threading mixed dislocations were observed to form arrays consisting of mixed dislocations with identical Burgers vectors. The minute lattice tilt and twist caused by the dislocation arrays were calculated based on dislocation spacing and confirmed with high resolution XRD measurements. SR-XRT analysis of grain boundaries and basal plane dislocations in ammonothermal GaN were also discussed. The structural quality of homoepitaxial GaN and heteroepitaxial GaN on patterned substrates was characterized by SR-XRT and XRD. The GaN layers were grown by metallo-organic vapour phase epitaxy (MOVPE) on ammonothermal GaN substrates, patterned sapphire substrates and substrates consisting of patterned MOVPE grown GaN layers on sapphire. SR-XRT is a technique especially suited for imaging the defect structure of materials with low crystalline defect density, whereas XRD is applicable to characterization of materials with higher defect density as well. SR-XRT measurements enabled imaging of individual dislocations and identification of different dislocation types.

KW - gallium nitride

KW - dislocations

KW - topography

KW - x-ray diffraction

KW - galliumnitridi

KW - dislokaatiot

KW - topografia

KW - röntgendiffraktio

KW - gallium nitride

KW - dislocations

KW - topography

KW - x-ray diffraction

M3 - Doctoral Thesis

SN - 978-952-60-5969-3

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Synchrotron radiation x-ray topography of crystallographic defects in GaN

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