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Identifier 000399721
Title Έλεγχος της πολικότητας επιταξιακού GaN πάνω σε υπόστρωμα Si(111)
Alternative Title Control of GaN polarity on Si(111) substrate
Author Τσικριτσάκη, Ελευθερία Ι.
Thesis advisor Γεωργακίλας, Αλέξανδρος
Reviewer Ηλιόπουλος, Ελευθέριος
Χατζόπουλος, Ζαχαρίας
Abstract The aim of this work is the control of III-Nitrides polarity on Si (111) substrates grown by plasma assisted molecular beam epitaxy (PAMBE). Depended on the applications, may be desirable Ga-face or N-face polarity. Two different groups of samples of thin films GaN (0001) were grown on Si (111) substrates. On those samples, not only growth conditions but also thickness of an initial nucleation layer AlN on the surface of the silicon substrate was changed. Their effectiveness on polarity, surfaces’ morphology, crystalline quality and electrical caracteristics of the growing material was examined. On the different AlN nucleation layers, the temperature of the substrate, the Al/N ratio of incident flow and the thickness of the AlN layer, were changed. On those thin films, HEMT AlN/GaN and AlGaN/GaN heterostructures were grown, so as to achieve the formation of a two dimensional electron gas (2DEG). The determination of GaN layers polarity was based on selective etching of N-face GaN, by dipping in KOH solution. It was also examined the occurence of C-V measurements, in order to define formation and place of 2DEG on heterostructures. Definition of polarity of epitaxial layers of those experiments showed that Ga-face polarity is achieved when AlN nucleation layer is used up to 2nm thickness. G-face polarity can be also achieved with an AlN nucleation layer of bigger thickness when it is grown on low temperature and N-rich conditions. N-face polarity is achieved by the growth of AlN nucleation layers with thickness of twenty-fifty nm on stichiometric conditions Al/N. Polarity of GaN layers and growth conditions of AlN nucleation layers, affected the morphology of the surface, the total crystalline quality and the electrical characteristics of GaN heterostructures.
Language Greek
Subject HEMT
III-Nitrides
III-Νιτρίδια
MBE
Issue date 2016-03-18
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
  Type of Work--Post-graduate theses
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