RF-MBE Growth Of III-Nitrides Heterostructures For Light Detecting Applications

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dc.contributor.authorMohd Yusoff, Mohd Zaki
dc.date.accessioned2017-01-24T00:58:00Z
dc.date.available2017-01-24T00:58:00Z
dc.date.issued2016-03
dc.description.abstractIn this research work, GaN p-n homostructures, AlN/GaN heterostructures, and AlxGa1-xN/Ga heterostructures were successfully grown on silicon (Si) (111) substrates by plasma-assisted molecular beam epitaxy (MBE) for photodetector applications. High purity gallium (7N) and aluminum (6N5) were used in the Knudsen cells and high purity nitrogen (7N) was supplied to 13.56 MHz radio frequency (RF) source to generate reactive nitrogen species. The nitrogen pressure and discharge power values were kept constant at 1.5x10-5 Torr and 300 W during this project, respectively. The surface morphology, structural and optical properties of all the samples were investigated by using reflection high energy electron diffraction (RHEED), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy, atomic force microscopy (AFM), high-resolution X-ray diffraction (HR-XRD), photoluminescence (PL), and Raman spectroscopy, respectively. For the growth of GaN p-n homostructures, Si and magnesium (Mg) were used as n- and p-dopants, respectively. The RHEED images indicated a good surface morphology of GaN p-n homostructure layers. According to XRD symmetric rocking curve ω/2ϴ scans of (0002) plane at room temperature, the full width at half-maximum (FWHM) of GaN p-n homostructures sample was calculated as 0.34o, indicating a good quality layer of GaN layer. The effect of the aluminum (Al) flux on the crystal quality of AlN/GaN heterostructures on Si (111) substrates was investigated. The thickness of 69.94 nm (AlN top layer) was obtained for good growth conditions giving the comparable FWHM of the XRD rocking curve of 0.46o (27.6 arcmin) when compared with other samples and previous works. It was found that the AlN/GaN heterostructures grown under low Al-flux has produced a good structural quality and low compressive strain value compared to the samples grown under high Al-fluxes. Two samples of low Alcontent Al0.11Ga0.89N/GaN and Al0.29Ga0.71N/GaN heterostructures were grown on Si substrates with FWHM of the XRD rocking curve of 0.62o and 0.52o, respectively. Using the conventional method, the strain values for samplesAl0.11Ga0.89N/GaN and Al0.29Ga0.71N/GaN heterostructures were calculated as (+) 0.248 % and (-) 0.121 %, respectively. These values are in good agreement with the studies by other researchers. The investigation of annealed Pt contact on AlN/GaN heterostructures at various annealing temperature for 10 min in nitrogen ambient was conducted in this project. It was found that the Schottky barrier heights (SBHs) and surface of contact changed with different annealing temperatures. Good results for SBH have been achieved for sample annealed at 800oC. Meanwhile, the characteristics of annealed Ni/Ag contact on Al0.11Ga0.89N/GaN heterostructures at various annealing temperatures for 10 min in oxygen ambient were also studied in this project. The results revealed that the best SBH value was obtained for the 700oC annealed Ni/Ag contact on sample. GaN p-n homostructures photodetector and metal-semiconductormetal (MSM) UV photodetectors of AlN/GaN and AlxGa1-xN/GaN heterostructures samples have been presented. The fabricated AlN/GaN heterostructures and AlxGa1- xN/GaN heterostructures based MSM for the UV photodetectors show good photoconductivity characteristics, suggesting that the samples have good carrier transport and crystalline properties.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/3540
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectAlN/GaN heterostructuresen_US
dc.titleRF-MBE Growth Of III-Nitrides Heterostructures For Light Detecting Applicationsen_US
dc.typeThesisen_US
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