We deposited 300-nm-thick GaN films on an amorphous glass substrate at a substrate temperature of 300 °C by using pulsed direct current (DC) sputtering. A ZnO buffer layer was utilized to improve the crystalline quality of the GaN films. Scanning electron microscopy results showed that the GaN thin films were grown along the c-axis and possessed a columnar structure. Atomic force microscopy results revealed that the GaN film deposited at a sputtering power of 75 W had the maximum grain size (24.1 nm). Room-temperature photoluminescence measurement of the GaN films indicated an ultraviolet near-band-edge emission at 365 nm and a Zn impurity energy transition level at 430 nm. In addition, X-ray diffraction conducted on the GaN films revealed a predominant (002) hexagonal wurtzite structure. The GaN film deposited at the sputtering power of 75 W demonstrated a high optical transmittance level of 88.5% in the wavelength range of 400–1100 nm. The material characteristics of the GaN films and ZnO buffer layer were studied using cross-sectional high-resolution transmission electron microscopy. The deposition of GaN films by using pulsed DC magnetron sputtering can result in high material quality and has high potential for realizing GaN-related optoelectronic devices on glass substrates.
Transparent conductive Ga-doped MgxZn1-xO (GMZO) films were deposited on sapphire at room temperature using radio-frequency magnetron sputtering with different RF powers. The thickness of all films was controlled at 300 nm, and the lowest resistivity was obtained at an RF power of 50 W. This study investigates the influence of the post-annealing process on the structural, electrical, and optical properties of the films using X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Hall measurement, optical transmission spectroscopy, photoluminescence (PL) spectra, and X-ray photoelectron spectroscopy (XPS) spectra. The XRD (002) peak intensity and the spectral linewidth enhanced monotonically as the annealing temperature rose to 700 degrees C, indicating improved crystallinity in the GMZO thin films. A low thin film resistivity (rho) of 5.69 x 10(-4) Omega cm was obtained, along with electron mobility (mu) and carrier concentrations (n) of 28.5 cm(2)/V s and 3.85 x 10(20) cm(-3), respectively. XPS measurements were conducted to investigate the mechanism of the reduced thin-film resistivity after high-temperature annealing. The increased density of oxygen vacancies could contribute to the reduced resistivity after high-temperature annealing. Meanwhile, a high optical transmittance of over 96.6% was demonstrated in a wavelength range between 350 and 1100 nm. (C) 2012 Elsevier B. V. All rights reserved.
SiGe metal-semiconductor-metal photodetectors (MSM-PDs) with a thin amorphous silicon (a-Si:H) passivation layer have been fabricated by an ultrahigh-vacuum chemical vapor deposition (UHVCVD) system. It was, found that the thin (30 nm) a-Si:H passivation layer could effectively suppress the dark current of SiGe MSM-PDs. As compared to the unpassivated devices, the dark current for devices with a-Si:H passivation layers was drastically reduced by 1.7 x 10(5), and the photo-to-dark current ratio was enhanced by 1.33 X 10(6). We attribute this result to the passivation effect of a-Si:H films on SiGe surfaces by hydrogen diffusion, which can compensate the dangling bonds on the SiGe surface.
In this work, we report the first study of the porous boron /delta/-doped Si superlattice. Visible photoluminescence (PL) with multiple peaks from the porous boron 6/spl delta/-doped Si superlattice was observed at room temperature. The multiple peaks of PL spectrum from the porous superlattice can be explained on the basis of interference from the periodic structure. The high-resolution double crystal x-ray diffraction (HRXRD) and scanning electron microscope (SEM) were used to investigate the dopant distribution and structure of these superlattices. In addition, theoretical transmittance of the porous superlattice with alternative refraction index was calculated to confirm the interference effect of the PL spectrum.
TRIM cascade calculations were utilized to simulate the defect production and energy deposition in the ion implanted silicon. A guide line for carbon ion beam defect engineering implant is obtained to reduce the size of residual defects in the high energy Ge+ preamorphized and low energy BF/sub 2/+ implanted silicon.
The effects of dilution gases on hydrogenated amorphous silicon nitride (a-SiN,:H) films were investigated in this study. Silarie and ammonia were used as the reactive species, while nitrogen, helium, hydrogen, and argon were used as the dilution gases in a plasma enhanced chemical vapor deposition system at a substrate temperature of 300'C. The total hydrogen concentrations for all a-SiN,:H films were observed to be smaller than 3.OxIO2,2 Cru-3. The dominant mode of electronic conduction would appear to be the Poole Frenkel emission deduced from the current versus voltage (I-V) measurements. The interface trap state density (Dit) which ranged from 3.4xlOII to 1.34012 cm-2eV-1 was evaluated by the C-V characteristics. The influences of dilution gases on a-SiN,:H were also investigated in an application to the performance of the hydrogenated amorphous silicon thin film transistors (a-Si:H TFrs). Analyses of the transfer characteristics of a-Si:H TFrs revealed that the density of deep gap states is 44012 cM-2&V-1 and the field effect mobility p FE) is changing from 0.37 cm'2/V-s to 1.45 cm2/V-s.
