Resonant excitation of surface plasmons in one-dimensional metallic grating structures at microwave frequencies

Grating-coupling phenomena between surface plasmons and electromagnetic waves were studied in the microwave spectrum using metallic gratings. Transmission measurements were carried out to observe the transmitted radiation around the surface plasmon resonance frequencies. Grating structures with subwavelength apertures were designed for transmission experiments. Measurements were made in the microwave spectrum of 10-37.5 GHz, corresponding to a wavelength region of 8-30 mm. The A1 samples had a grating periodicity of 16 mm. A 2 mm wide subwavelength slit was opened for transmission samples. Samples with one/double-sided gratings displayed remarkably enhanced transmission and directivity with respect to the reference sample without gratings. The experimental results agreed well with theoretical simulations. ∼50% transmission at 20.7 mm, ∼25-fold enhancement, and ±4° angular divergence were achieved with a ∼λ/10 aperture. © 2005 IOP Publishing Ltd

Growth and characterization of SiC epitaxial layers on Si- and C-face 4H SiC substrates by chemical-vapor deposition

High-quality Schottky junctions have been fabricated on n-type 4H SiC epitaxial layers grown by chemical-vapor deposition on C- and Si-face substrates in order to understand the effect of growth direction on the growth mechanism and formation of defects. Atomic force microscopy analysis showed dramatic differences between the surfaces of SiC epilayers grown on C and Si faces. There was a significant step bunching in the SiC grown on Si-face substrates. Current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS) measurements were carried out on the Schottky junctions to analyze the junction characteristics. The Schottky junctions on C-face SiC showed larger barrier heights than those on Si-face SiC, showing that each face has a different surface energy. The barrier heights of Ni Schottky junctions were found to be 1.97 and 1.54 eV for C-face and Si-face materials, respectively. However, the deep-level spectra obtained by DLTS were similar, regardless of the increased surface roughness of the Si-face 4H SiC

Effect of C∕Si ratio on deep levels in epitaxial 4H–SiC

Changing the ratio of carbon to silicon during the epitaxial 4H–SiC growth is expected to alter the dominant deep level trap, which has been attributed to a native defect. The C∕Si ratio was changed from one to six during epitaxialgrowth of SiC. Diodes fabricated on the epitaxial layer were then characterized using current-voltage and deep level transient spectroscopy. The single peak at 340K (Z1/Z2 peak), was deconvolved into two traps, closely spaced in energy. The concentration of one of the Z1/Z2 traps decreased with increasing C∕Si ratio. This result opposes theoretical predictions of carboninterstitial components, and supports assignment to a silicon antisite or carbonvacancy relationship. The concentration of the second component of the peak at 340K did not depend on the C∕Si ratio, which would indicate an impurity in an interstitial site

Properties Of Isotype N-Zno/N-Gan Heterostructures Studied By I-V-T And Electron Beam Induced Current Methods

Electrical properties of isotype n-ZnO/n-GaN heterostructures obtained by radio-frequency sputtering of ZnO films on GaN layers are studied by means of temperature dependent current-voltage (I-V-T) characterization and electron beam induced current (EBIC) measurements. The n-ZnO/n-GaN diodes showed highly rectifying behavior with a forward and reverse current ratio of about 10 6 at 5V. From the analysis of I-V-T measurements, a conduction band offset of ∼0.62eV was derived. From EBIC measurements, theminority carrier diffusion length of ZnO was estimated to lie in the range 0.125-0.175νm, while an activation energy was derived as 0.462 0.073V and was attributed to the traps. © IOP Publishing Ltd

Current-Transport Mechanisms Of Isotype N-Zno/N-Gan Heterostructures

Electrical properties of n-ZnO/n-GaN isotype heterostructures prepared by rf-sputtering of ZnO films on GaN layers which in turn grown by metal-organic vapour phase epitaxy are discussed. Current-voltage (I-V) characteristics of the n-ZnO/n-GaN diodes exhibited highly rectifying characteristics with forward and reverse currents being ∼1.43×10-2 A/cm2 and ∼2.4×10-4 A/cm2, respectively, at ±5 V. From the Arrhenius plot built representing the temperature dependent current-voltage characteristics (I-V-T) an activation energy 0.125 eV was derived for the reverse bias leakage current path, and 0.62 eV for the band offset from forward bias measurements. From electron-beam induced current measurements and depending on excitation conditions the minority carrier diffusion length in ZnO was estimated in the range 0.125-0.175 μm,. The temperature dependent EBIC measurements yielded an activation energy of 0.462 ± 0.073 V

Growth and characterization of SiC epitaxial layers on Si- and C-face 4H SiC substrates by chemical-vapor deposition

High-quality Schottky junctions have been fabricated on n-type 4H SiC epitaxial layers grown by chemical-vapor deposition on C- and Si-face substrates in order to understand the effect of growth direction on the growth mechanism and formation of defects. Atomic force microscopy analysis showed dramatic differences between the surfaces of SiC epilayers grown on C and Si faces. There was a significant step bunching in the SiC grown on Si-face substrates. Current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS) measurements were carried out on the Schottky junctions to analyze the junction characteristics. The Schottky junctions on C-face SiC showed larger barrier heights than those on Si-face SiC, showing that each face has a different surface energy. The barrier heights of Ni Schottky junctions were found to be 1.97 and 1.54 eV for C-face and Si-face materials, respectively. However, the deep-level spectra obtained by DLTS were similar, regardless of the increased surface roughness of the Si-face 4H SiC. (c) 2005 American Institute of Physics.open1189sciescopu

Effect of C/Si ratio on deep levels in epitaxial 4H-SiC

Changing the ratio of carbon to silicon during the epitaxial 4H-SiC growth is expected to alter the dominant deep level trap, which has been attributed to a native defect. The C/Si ratio was changed from one to six during epitaxial growth of SiC. Diodes fabricated on the epitaxial layer were then characterized using current-voltage and deep level transient spectroscopy. The single peak at 340 K (Z1/Z2 peak), was deconvolved into two traps, closely spaced in energy. The concentration of one of the Z1/Z2 traps decreased with increasing C/Si ratio. This result opposes theoretical predictions of carbon interstitial components, and supports assignment to a silicon antisite or carbon vacancy relationship. The concentration of the second component of the peak at 340 K did not depend on the C/Si ratio, which would indicate an impurity in an interstitial site.open112326sciescopu