Fabrication and Characterisation of III-V Semiconductor Nanostructures

Bjerring, Mads Blach Rossen ; Bonde, Hans Christian ; Sandager, Matilde Kammer

4. term (FYS10)

Physics, Master

2021

79

Dette speciale undersøger fremstilling og karakterisering af III-V halvledernanostrukturer med fokus på AlN og GaN, motiveret af deres potentiale i f.eks. LEDer, FETer og piezoelektrisk energihøstning. Nucleationsfasen og vækst af AlN blev studeret ved reaktiv DC magnetronsputtering, katalysator-assisteret dannelse af nanostrukturer blev afprøvet med MOCVD, og MBE-voksede GaN-nanowires blev strukturelt og elektrisk karakteriseret. Analyse med AFM, SEM, KPFM og EDX viser, at ramificerede AlN-øer dannet under sputtering har “magiske” trinhøjder i skridt på cirka 5,3 nm og en overfladedækning, der stabiliserer omkring 14 %. Ø-dannelsen tilskrives sandsynligvis den indledende Al-forsputtering til target-rensning, hvilket indikerer behov for procesjustering for at opnå ren AlN. Fritstående kolonnære AlN-nanowires blev ikke opnået ved sputtering; i stedet fremkom blomsterlignende strukturer med lamellære komponenter, og systematiske parameterstudier gav et grundlag for en strategi til bedre kontrol af AlN-væksten. MOCVD gav ligeledes blomsterlignende morfologier, hvilket kræver yderligere optimering af vækstparametre. MBE-voksede GaN-nanowires udviste temperaturafhængige overfladedensiteter og blandet polaritet med både Ga- og N-facetter. Arbejdet bidrager med indsigt i de tidlige vækststadier og processtyring, som er nødvendig for at fremme lodret nanowire-dannelse i III-V materialer.

This thesis investigates the fabrication and characterization of III–V semiconductor nanostructures focusing on AlN and GaN, motivated by their potential in applications such as LEDs, FETs, and piezoelectric energy harvesting. The nucleation stage and growth of AlN were examined using reactive DC magnetron sputtering, catalyst-assisted formation of nanostructures was tested via MOCVD, and MBE-grown GaN nanowires were structurally and electrically characterized. Analyses by AFM, SEM, KPFM, and EDX reveal that ramified AlN islands formed during sputtering exhibit “magic” step heights of approximately 5.3 nm and a surface coverage that stabilizes around 14%. Island formation is most likely linked to preliminary Al pre-sputtering for target cleaning, indicating that process adjustments are needed to achieve pure AlN. Free-standing columnar AlN nanowires were not obtained by sputtering; instead, flower-like lamellar structures appeared, and systematic parameter tests provided a basis for a strategy to better control AlN growth. MOCVD similarly produced flower-like morphologies, requiring further tuning of growth parameters. MBE-grown GaN nanowires showed temperature-dependent surface densities and mixed polarity with both Ga- and N-facets. The work offers insights into early growth stages and process control necessary to promote vertical nanowire formation in III–V materials.

[This summary has been generated with the help of AI directly from the project (PDF)]

Sputtering ; MOCVD ; MBE ; Nanowire ; GaN ; AlN ; Ramified Island

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