Papers by Keyword: Carrier Concentration

Abstract: Undoped ZnO, Gd-doped ZnO, and (Al, Gd) co-doped ZnO thin films were synthesized using the co-sputtering technique on a glass substrate. XRD data confirmed all the films are hexagonal structures with dominant (002) diffraction peaks. There are no secondary phases or other peaks detected except for ZnO which proves well incorporation of Gd³⁺ and Al³⁺ ions into ZnO ions for Gd and (Al, Gd) co-doping ZnO thin films. The EDX analysis shows the composition of Al, Gd, Zn, and O for (Al, Gd) co-doped ZnO thin films considering the successfully doping of Gd and Al into ZnO structure by this deposition method. As compared with undoped ZnO and Gd-doped ZnO, the electrical properties of (Al, Gd) co-doped ZnO showing a good enhancement of carrier concentration (2.34 x 10²⁶ m^-3) and electrical conductivity (1.41 x 10⁵ Ωm^-1) whereas the resistivity is low about 7.11 x 10⁴ Ωcm.

Abstract: We investigated the spatial distribution of carrier concentration in n-type 4H-SiC grown by the solution method from the peak frequency of the longitudinal optical phonon-plasmon coupled (LOPC) mode of the Raman spectra on the surface. The carrier concentration at the position of the smooth terrace was higher than the carrier concentration at the position where the macrosteps were formed. This indicates the nitrogen incorporation efficiently occurs on the smooth surface where the density of macrosteps is relatively low. The different incorporation of nitrogen depending on the surface morphology can be understood from the view point of the adsorption time of impurity on the terrace. The present result implies that the uniform surface morphology is necessary to achieve uniform doping concentration in SiC crystal.

Abstract: This paper presents the improvement of intrinsic carrier concentrations in the active layer of solar cell structure using Indium Nitride quantum dot as the active layer material. We have analyzed effective density of states in conduction band and valance band of the solar cell numerically using Si, Ge and InN quantum dot in the active layer of the solar cell structure in order to improve the intrinsic carrier concentration within the active layer of the solar cell. Then obtained numerical results were compared. From the comparison results it has been revealed that the application of InN quantum dot in the active layer of the device structure improves the effective density of states both in conduction band and in the valance band. Consiquently the intrinsic carrier concentration has been improved significently by using InN quantum dot in the solart cell structure.

Abstract: The guidelines necessary to improve the n-type doping uniformity on C-face epitaxial growth of 4H-SiC have been examined as far as the practical throughput is maintained, e.g. 3×150 mm wafers with the growth rate higher than 20 μm/h. The flow-channel enlargement was carried out and the effect was estimated by temperature distribution estimation performed by hydrogen etching. Also, effective C/Si was simulated with the temperature distribution obtained from the hydrogen etching experiments. As a result, positional agreement was found between the region where carrier concentration begins to increase and the drastic drop in temperature and the effective C/Si ratio.

Abstract: Bi-2212 bulks have been fabricated by spark plasma sintering technique with the Bi-2212 precursor powders synthesized by co-precipitation process. The Al₂O₃ dopants were added into the precursor powders during the sintering process. The lattice parameters of Bi-2212 increased with Al content, suggesting that Al³⁺ ions entering into the lattice as interstitial ions due to the small ion radii. The carrier concentration has been calculated with measured room temperature thermopower values. The change of carrier concentration can be attributed to the changes of both Al and oxygen contents in the lattice. Therefore, by Al doping the samples have been tuned into optimal doping region with maximum critical temperature of 86K. The appearance of Al interstitial ions in the lattice caused certain amount of point defects, which acted as pinning centers. Therefore the flux pinning properties have been enhanced in the bulks, and obvious improvements of critical current density for over 55% have been obtained at 4.2K self-field.

Abstract: 3C-SiC have been epitaxially grown through vapour phase expitaxy under a different grow conditions. Key electrical properties of these SiC layers have been characterised by fabrication and measurement of metal-SiC-metal devices. The electrical properties of SiC grown at different conditions have been analysed based on their structural and crystalline quality.

Abstract: Tin oxide SnO2 thin films are deposited by atmospheric pressure chemical vapor deposition APCVD technique. The electrical properties of the deposited films and the influence of the temperature ranging from room temperature to 500°C are analyzed by Hall measurement technique. The negative value of the hall constant indicates that the obtained tin oxide thin films are an N type semiconductor. The value of the mobility and the carrier concentration are 21 cm²/ V. sec and 1,50. 1020 cm-3 respectively. These films present an optical reflectance less than 20%.The change of the surface morphology due to the heat treatment is characterized by the scanning electronic microscopy SEM and the transmission electronic microscopy TEM. The films have a polycrystalline aspect. A post annealing at 500°C improves their morphology.

Abstract: We present the study of the electrical properties of monolayer MoS₂ in terms of semiconductor theory. The free electron and hole concentrations formulas in two-dimensional (2D) semiconductors have been developed based on three-dimensional (3D) semiconductors theory, and derived the intrinsic carrier concentration equation of 2D system. Using these equations, we simulated the intrinsic carrier concentration in monolayer MoS₂ with temperature. The intrinsic carrier density in monolayer MoS₂ increases exponentially with temperature, but it lows a few orders of magnitude than that of 3D semiconductor. It means that monolayer MoS₂ based devices can operated at very high temperatures. Accordingly, the conductivity and resistivity were simulated for 2D MoS₂, the former increases exponentially while the latter decreases with temperature or carrier concentration.

Abstract: In semiconductor industry, carrier concentration of a semiconductor material needs to be measured. Theoretical computation is complex and has its limitation. Experiment measurement always needs complicated and expensive instruments. Here, a new method for measuring the carrier concentration of silicon wafer was put forward. The dependen curve of thermoelectromotive force on temperature was graphed. The results showed that when temperature is below 460K, thermoelectromotive force is proportional to temperature of the hot probe. With the help of Origin software, slope of curve was obtained.Accoeding to related formula,the doping concentartion and it’s uniformity were figured out finally .Compared with other similar methods, this method is more simplified and thet equipment is cheaper.

Abstract: We report the electrical properties of the InSbN alloys fabricated by two-step implantation of nitrogen ions into InSb wafers, characterized by Hall measurements. The alloy with higher implanted dose shows lower electron concentration due to the acceptor nature of nitrogen. At temperatures below 150 K, the electron concentration does not change and follows an exponential relation at above 200 K. The Hall mobility in all samples monotonically decreases with the increase of temperature, indicating the phonon dominating scattering mechanism. The annealing results reveal that annealing temperatures up to 598 K make the carrier concentration lower due to the reduction of donor-type defects caused by ion implantation and the acceptor nature of nitrogen.