Papers by Author: Y. Shishkin

Abstract: A lightly doped n-type homo-epitaxial layer was grown by CVD onto a heavily doped n-type 4H-SiC substrate for which half of the surface had been made porous by photoelectrochemical etching. Raman spectra are obtained in the optic phonon region using three scattering geometries. An effective medium model for the porous layer is used to assist in the interpretation of the spectra. This work demonstrates that the contributions to the Raman spectra of the various layers in a sample with multiple 4H-SiC layers can be extracted.

Abstract: Growth rates from 10 to 38 μm/h of single crystal 3C-SiC on planar Si (001) substrates have been obtained in a low-pressure horizontal hot-wall CVD reactor. The propane-silanehydrogen gas chemistry system with HCl added as a growth additive, which allows an increased amount of silane to be introduced into the reactor during growth, was used. The 3C-SiC film growth rate versus silane mole fraction was found to be a linear function in the range from 0.43x10-3 to 1.50x10-3. Nomarski optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy and X-ray diffraction were used to characterize the deposited layers. The X-ray rocking curve taken on the (002) diffraction plane of a 12 μm thick 3CSiC (001) layer displayed a FWHM of 360 arcsec, which indicates the films are mono-crystalline.

Abstract: Crystal growth of 6H-SiC in two non-basal directions is reported. The two explored surfaces are the {1-103} plane, named qC-face, and the {1-10-3} plane, named qSi-face. The asgrown bulk surfaces exhibit a smooth structure with a small ridging effect originating from the miscut of the seed crystals. Layers, epitaxially grown on the chemically-mechanically polished qCface, nicely replicate the original crystal structure and show no sign of polytype mixing. Lowtemperature photoluminescence measurements collected on the epilayers exhibit near bandedge spectral characteristics indicative of good quality 6H-SiC.

Abstract: A fully-comprehensive three-dimensional simulation of a CVD epitaxial growth process has been undertaken and is reported here. Based on a previously developed simulation platform, which connects fluid dynamics and thermal temperature profiling with chemical species kinetics, a complete model of the reaction process in a low pressure hot-wall CVD reactor has been developed. Close agreement between the growth rate observed experimentally and simulated theoretically has been achieved. Such an approach should provide the researcher with sufficient insight into the expected growth rate in the reactor as well as any variations in growth across the hot zone.

Abstract: A hetero-epitaxial 3C-SiC growth process in a low-pressure hot-wall CVD reactor has been developed on planar Si (100) substrates. The growth rate achieved for this process was about 10 μm/h. The process consists of silane/propane/hydrogen chemistry with HCl used as a growth additive to increase the growth rate. 3C-SiC has also been grown on 22, 52 and 123 +m deep etched MEMS structures formed by DRIE of (100) Si at a rate of about 8 +m/h. Secondary electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) were used to analyze the quality of the 3C-SiC films.

Abstract: Hot-wall chemical vapor deposition has been used to epitaxially grow SiC layers on porous n-type 4H-SiC substrates. The growth was carried out at different speeds on porous layers of two different thicknesses. The quality of the SiC films was evaluated by X-ray diffraction and photoluminescence techniques. Based on the measurements, both the growth speed and the thickness of the porous layer buried underneath the epilayers do not appear to influence the structural integrity of the films. The intensity of the near bandedge low temperature photoluminescence appears stronger by a factor of two in films grown on porous layers.

Abstract: A 4H-SiC epitaxial growth process has been developed in a horizontal hot-wall CVD reactor using a standard chemistry of silane-propane-hydrogen, producing repeatable growth rates up to 32 μm/h. The growth rate was studied as a function of pressure, silane flow rate, and growth time. The structural quality of the films was determined by X-ray diffraction. A 65 μm thick epitaxial layer was grown at the 32 μm/h rate, resulting in a smooth, specular film morphology with occasional carrot-like and triangular defects. The film proved to be of high structural quality with an X-ray rocking curve FWHM value of the (0004) peak of 11 arcseconds.

Abstract: A brief historical development of porous SiC and GaN is given. SEM images of nine porous morphologies in 4H, 6H and 3C SiC are shown along with anodization details. Similarly, two porous GaN morphologies are presented. Applications and future prospects are discussed.

Abstract: The effect of thermal treatments in nitric oxide (NO) on the paramagnetic defects at the 4H-SiC/SiO2 interface are analyzed by EPR in oxidized porous samples. The results on ultrathin thermal oxides show that the NO treatment at 1000°C is insufficient for an efficient reduction of the two dominant paramagnetic interface defects: PbC centers and carbon clusters. From the NRA and XPS analysis of bulk samples treated under the same conditions we attribute the weak effect to the low nitrogen concentration of only 1% at the interface.

Abstract: The defects at the 3C-SiC/SiO2 interface have been studied by X-band EPR spectroscopy in oxidized porous 3C-SiC. One interface defect is detected; its spin Hamiltonian parameters, spin S=1/2, C3V symmetry, g//=2.00238 and g⊥=2.00317, central hyperfine interaction (CHF) with one carbon atom and AB//[001]=48G and superhyperfine (SHF) interaction with three equivalent Si neighbour atoms and TB//[001]=12.4G, allow us to attribute the center to a sp3 coordinated carbon dangling bond center, PbC.