Papers by Keyword: Si Substrate

Abstract: This paper introduced an accurate empirical model for the thermal resistance of a single-finger AlGaN-GaN high electron mobility transistor (HEMT) on three different substrates including Sapphire, SiC and Si. The model reckons the constant thermal conductivity of GaN and substrate, thickness of host substrate layers, gate length (Lg) and width (Wg). The model plausibility is verified by comparing it with DC channel temperature measurement method and charge controlled based device modeling which agrees very favorable observation of the model data. Having nimble expression for the channel temperature is of inordinate importance in the field of designers of power device and monolithic microwave integrated circuits. Proposed model gives a variety of inquiries that would be impossible or impractical to do using time-consuming numerical simulations.

Abstract: Gallium nitride (GaN) transparent and semiconducting thin films were prepared on an amorphous glass substrate by a reactive sputtering method using Ar-N₂ radio-frequency plasmas. In addition, GaN thin films were prepared on amorphous silicon-dioxide (SiO₂) layer-deposited Si (111) single-crystalline substrates by a reactive evaporation method. Optical transmission properties, electrical properties, and crystallinities of the films prepared on the glass substrate were investigated as a function of the mixing ratio of the reactive sputtering gases. On the other hand, variations in the crystallinities of the films prepared on the amorphous SiO₂ layer-deposited Si (111) substrates were investigated as a function of the thickness of the amorphous SiO₂ layers.

Abstract: To ascertain physical mechanism of charge transport in Si/SiO_x structures with Ge nanoclusters the measurements of their DC and AC conductivity, and also the low-frequency measurements were performed. It was revealed that in the temperatures range 110 – 250 K the characteristics measured are governed by the hopping mechanism of charge transport. The model proposed suggests that the charge hopping becomes possible due to the band of localized states inducing in the bandgap of silicon substrate when Ge nanoclusters are introduced. The model was used to estimate some parameters of hopping transport. Also, the analysis of the low-frequency noise measured for Si/SiO_x structures with Ge nanoclusters allowed to ascertain the mechanism of charge hopping resulting in strong temperature dependence of the 1/f noise measured.

Abstract: This paper presents the device-technological simulation of local 3D SOI structures. These structures are created by use microcavities under surface of silicon wafer. Is shown that proposed microcavities could be use as a constructive material for CMOS transistor array on the bulk silicon and 3D SOI-CMOS transistor array, as well as the sensitive elements and their combinations. Such structures allow creation and monolithic integration the CMOS, SOI-CMOS circuits and sensitive elements for IC and SoC.

Abstract: We report on the study on effect of Ga pre-deposition rate on GaAs nanowires grown by self-assisted vapor-liquid-solid (VLS) method. Ga droplets were initially deposited on the surface of Si(111) substrates covered with thin layer of SiO₂. The nanowires were grown by molecular beam epitaxy (MBE). Dependency of structural of nanowires on Ga pre-deposition rate is investigated by Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray Diffraction Analysis (XRD). The experimental results show that the different in Ga pre-deposition rate significantly affect the surface morphology of samples. Growth rate and the density of nanowires strongly depends on the Ga pre-deposition rate.

Abstract: Mg_xZn_1-xO films with hexagonal structure are prepared by radio frequency (rf) magnetron sputtering on Si substrate. The refractive indices and absorption coefficients of these films in the wavelength range from 300 to 800nm are determined by using ellipsometry at room temperature. The results show that the refractive index increases as the wavelength decreases in the transparent region (400-800nm). It reaches its maximum value around 340nm and 331nm, which is close to the fundamental absorption edge. Then the refractive index decreases as the wavelength gets shorter. The value of the refractive index is also a function of the Mg content. The higher the Mg content is in the film, the smaller the refractive index of the film is in the wavelength range from 330nm to 850nm. The band gap energy of the Mg_xZn_1-xO film is obtained by analyzing its absorption spectrum. An increase in the Mg content causes the fundamental absorption edge to shift toward shorter wavelength. In addition, UV and strong blue emission have been observed when the Mg_xZn_1-xO film is excited with light wave of 260nm at room temperature, and the emission mechanism is discussed.

Abstract: The influence of Mn/Ga solution on the characteristics of solid composition and microstructure of GaN:Mn thin film was studied. GaN:Mn thin films were deposited on Si (111) substrate by the Chemical Solution Deposition (CSD) method using the spin coating technique. Variations of the Mn/Ga mole fraction were 4%, 6%, 8%, and 10% respectively. The GaN:Mn thin films were then heated at a temperature of 900°C for 2 hours in an N₂ environment with a constant flow rate of 120 sccm. Atomic composition, crystal structure, and surface morphology of GaN:Mn thin films were characterized using X-Ray Diffraction (XRD), Energy Dispersive of X-ray (EDX), and Scanning Electron Microscope (SEM). EDX results showed that the larger the Mn/Ga mole fraction solution, the higher the Mn At percentage is. The correlation of At Mn percentage and Mn/Ga solution mole fraction is represented by the formula y = 0.023x³ - 0.352x² - 1.742x -2.81. All of the GaN:Mn thin films still have nitrogen vacancy, carbon impurity and maintain the wurtzite polycrystalline structure. Lattice parameter a, which is in the range of 3.2077Å – 3.2621Å, and lattice parameter c, which is in the range of 5.1094Å – 5.3038Å, depend on Mn atomic percentage of the film. The Root Mean Square (RMS) of GaN:Mn thin film surface roughness is in the range of 15.3nm – 29.90nm. The grain size for the 6% Mn/Ga mole fraction thin film is homogeneous.

Abstract: The epitaxial growth of Gallium Nitride (GaN) on 2 inch Si (1 1 1) substrates was investigated, and it was found that by inserting a surface nitridation layer prior to Aluminum Nitride (AlN) nucleation upon substrate, the discoid defects and cracks on the surface were suppressed. Furthermore, compared with the GaN epitaxial layer grown without nitridation, the one with a 30 sec. nitridation layer showed a twice brighter integrated photoluminescence (PL) spectra intensity and a (0 0 2) High-resolution X-ray diffraction (HRXRD) curve width of 13.6 arcminute. The crystalline quality of GaN epitaxial layer became worse when the nitridation time exceeded a critical value, and even more cracks appeared on the surface although no discoid defect appeared anymore.

Abstract: SF₆/O₂ plasma surface texturing was employed to pretreat Si substrate for achieving enhanced diamond nucleation density. Surface roughness of the textured Si was found to be strongly dependent on the process pressure and normalized roughness values in the range of 2-16 were obtained. Remarkably enhanced nucleation densities of ~10¹⁰ cm^-2 compared to conventional mechanical abrasion were obtained after seeding for the surface textured Si substrates. Raman spectroscopy revealed that ultrananocrystalline diamond films with grain size below 10 nm were grown on the surface textured Si.

Abstract: In this paper, a color chart was defined for thin SiC films grown on Si substrates. For SiC films thinner than 500 nm, the surface color was observed using an optical microscope with the incident light normally illuminated on the SiC surface. An image of the surface was then taken by a camera attached to the optical microscope and the surface color was defined using RGB code. For SiC films thicker than 500 nm, the image taken by the camera did not represent the real color of the SiC film. Therefore, for these thicker SiC films, the colors were defined by observing the films under daylight fluorescent lighting by naked eyes. It was found that the colors of the SiC films vary periodically as the thickness increased. No color saturation was found for SiC films up to 1185 nm thick.