MOCVD growth and characterization of al-rich ALN/ALGAN epilayers and quantum wells

dc.contributor.authorAl Tahtamouni, Talal Mohammed Ahmad
dc.description.abstractThe correlation between polarity and material quality of un-doped Al[0.81subscript]Ga[0.19subscript]N was studied. The overall material quality is significantly influenced by the growth polarity. The epilayers with aluminum-polarity have a much higher crystalline quality and better surface morphology than those of nitrogen-polarity. Nitrogen-polar growth more readily incorporates unintentional impurities. A-plane AlN epilayers have been grown on r-plane sapphire substrates. The orientation and high crystalline quality were confirmed by x-ray diffraction (XRD) [Theta]-2[Theta] scan exhibiting a reflection peak at 2[Theta] = 59.4[0superscript] and rocking curve of the (110) reflection having a line width of 940 arcsec. Room temperature photoluminescence (PL) spectroscopy showed that the surface emission intensity of a-plane AlN epilayers is comparable to that of c-plane AlN. PL spectra of Mg-doped a- and c-plane AlN revealed that the Mg level in both a- and c-plane AlN is identical and is about ~ 0.5 eV. Identically designed a-plane and c-plane AlN/A1[0.65subscript]Ga[0.35subscript]N QWs have been grown on a-and c-plane AlN/Al[2subscript]O[3subscript] templates respectively, and their PL emission properties were studied. Low temperature PL characteristics of a-plane QWs are primarily governed by the quantum size effect, whereas those of c-plane QWs are significantly affected by the polarization fields. The growth of AlN epilayers on SiC substrates was investigated. A smooth, crack free AlN epilayer with high optical and crystalline quality was achieved. Because of its high quality, AlN was used as active layer in a hybrid Schottky photodetector. Highly conductive Si-doped Al[subscript0.75]Ga[0.25subscript]N alloys were grown on AlN/SiC templates. The effects of using Indium as a surfactant during the growth of Si-doped Al[0.75subscript]Ga[0.25subscript]N epilayers at relatively high temperature 1050 [degrees]C were studied. Indium significantly increases the doping efficiency as shown by RT Hall measurements. RT PL measurements show a clear correlation between emission intensity of the defect related transition and indium flow rate. P-type conductivity has been obtained in beryllium doped GaN by MOCVD. The activation energy of the beryllium acceptor was estimated to be 118 [plus or minus] 4 meV, which is about 40 meV less than the activation energy of the Mg acceptor in GaN.en
dc.description.advisorHongxing Jiangen
dc.description.degreeDoctor of Philosophyen
dc.description.departmentDepartment of Physicsen
dc.publisherKansas State Universityen
dc.subjectNitrides growthen
dc.subjectMetal organic chemical vapor depositionen
dc.subject.umiPhysics, Condensed Matter (0611)en
dc.titleMOCVD growth and characterization of al-rich ALN/ALGAN epilayers and quantum wellsen


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