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Synchrotron X-ray Characterization of Structural Defects in III-Nitride Wide Bandgap Semiconductors

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dc.contributor.advisor Dudley, Michael en_US
dc.contributor.advisor Raghothamachar, Balaji en_US
dc.contributor.author Wu, Shuang en_US
dc.contributor.other Department of Materials Science and Engineering en_US
dc.date.accessioned 2017-09-20T16:42:33Z
dc.date.available 2017-09-20T16:42:33Z
dc.date.issued 2017-05-01 en_US
dc.identifier.uri http://hdl.handle.net/11401/76165 en_US
dc.description 56 pgs en_US
dc.description.abstract III-nitrides have long been viewed as promising semiconductor materials for their wide-band gap and high efficiency for emitting light. They have been widely used in electronic and optoelectronic devices, even in the extreme environments such as high frequencies, high voltages and high temperatures. Despite their favorable properties, their performance is strongly affected by factors; such as the growth method employed and consequently the defect types generated and their quantity. In this thesis, the wide bandgap III-nitrides, aluminum nitride (AlN) and gallium nitride (GaN) will be discussed in the aspect of structure, properties and defects characterization. The density of defects, particularly basal plane dislocations and threading edge and screw dislocations, will be measured across multiple wafers and analyzed in order to gain insights into origins of these defects with respect to the growth process employed. Other defects like low angle grain boundaries and prismatic slip bands are also observed and analyzed. In this study, synchrotron white beam and monochromatic X-ray topography are the main techniques employed to characterize samples, with Nomarski optical microscopy used in a complementary manner. For physical vapor transport (PVT) grown AlN wafers, the distribution of basal plane dislocations and threading dislocations imaged and analyzed synchrotron X-ray topography reveals a wide range of densities from as low as 1.7×102cm-2 to greater than 106cm-2, the resolution limit for X-ray topography techniques. For basal plane dislocations (BPDs), the average density is 1.6747×104 cm-2. As for threading dislocations (TDs), both screw and edge, the average dislocation density is about 1.5515×104 cm-2 ranging from a low of 3.00×102cm-2 to a high of 4.477×104cm-2. These differences among the wafers, is clearly attributable to variations in growth conditions. For hydride vapor phase epitaxy (HVPE) grown GaN wafers on ammonothermal GaN substrates, the threading dislocations and basal plane dislocations in c-plane wafers are observed clearly by synchrotron X-ray topography. The dislocation density of BPDs is relatively low and they are distributed non-uniformly. The average BPD density for c-plane samples is about 1.509×104cm-2 and for TEDs, the dislocation density is of the order of a few 103cm-2, and TSD density is about 102cm-2. Axial wafers with a-plane and m-plane orientations have been characterized and reveal the evolution of defects due to variations in growth conditions in the c-axis growth directions. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Materials Science en_US
dc.subject.other defects, III-nitrides, semiconductor, synchrotron X-ray topography en_US
dc.title Synchrotron X-ray Characterization of Structural Defects in III-Nitride Wide Bandgap Semiconductors en_US
dc.type Thesis en_US
dc.mimetype Application/PDF en_US

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