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1	Investigation of PAMBE Grown InN on Different Buffer Layers Jiang, Zhi-Wei 23 March 2006 (has links) In this thesis, we study high quality InN films grown on sapphire (0001) by plasma-assisted molecular beam epitaxy (PAMBE). We used double layers methods to reduce lattice mismatch successfully. In this experiment, we have two series of samples, about series of A use low temperature GaN (LT-GaN) as the buffer layer as compared with series of B use high temperature AlN (HT-AlN) as the buffer layer. By in situ reflection high-energy electron diffraction (RHEED), we got film¡¦s surface situation. Surface morphology of the samples was observed by atomic force microscope (AFM). By high resolution X-ray diffraction (HR-XRD) methods was analyzed quality and composition of InN films. Van der Pauw method (Hall) was used to determine carrier concentration and mobility. The optical properties of InN films under different growth conditions were investigated by photoluminescence (PL). By changing growth temperature of these samples, we found the series of A having some fine characters as the InN(0002) rocking curve was 343 arcsec and InN(10-12) rocking curve was nearly 1000 arcsec. The mobility and carrier density of these samples were approximately 1000 cm2/Vs and 3 x 1018 cm-3 by Van der Pauw method. KOH etching XRD InN MBE AFM PL
2	A Study on the Nature of Anomalous Current Conduction in Gallium Nitride Spradlin, Joshua K. 01 January 2005 (has links) Current leakage in GaN thin films limits reliable device fabrication. A variety of Ga and N rich MBE GaN thin films grown by Rf, NH3, and Rf+ NH3, are examined with electrical measurements on NiIAu Schottky diodes and CAFM. Current-voltage (IV) mechanisms will identify conduction mechanisms on diodes, and CAFM measurements will investigate the microstructure of conduction in GaN thin films. With CAFM, enhanced conduction has been shown to decorate some extended defects and surface features, while CAFM spectroscopy on a MODFET structure indicates a correlation between extended defects and field conduction behavior at room temperature. A remedy for poor conduction characteristics is presented in molten KOH etching, as evidenced by CAFM measurements, Schottky diodes, and MODFET's. The aim of this study is to identify anomalous conduction mechanisms, the likely cause of anomalous conduction, and a method for improving the conduction characteristics. Keywords: 111-Nitride, 111-V, Gallium Nitride, GaN, Electrical Properties, Conduction, Conductivity, Mobility, Hall Measurements, Resistivity, Schottky Diode, Modulation Doped Field Effect Transistor (MODFET), Conductive Atomic Force Microscopy (AFM), Defects, Molten Potassium Hydroxide (KOH) etching, Silvaco, Atlas, and Illumination. photoluminescence SEM DLTS CAFM mobility KOH etching MODFET resistivity III-Nitride III-V Hall measurements silvaco schottky diode illumination polarization MBE MOCVD HVPE semiconductor Electrical and Computer Engineering Engineering

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Investigation of PAMBE Grown InN on Different Buffer Layers

A Study on the Nature of Anomalous Current Conduction in Gallium Nitride