Papers by Keyword: Barrier Height

Abstract: This study investigates the role of ultra-thin conductive Indium-Tin-Oxide (ITO) as an interlayer at the Metal-SiC (MS) junction to lower the overall specific contact resistance (SCR) for source drain metallization applications on n-type 4H-SiC substrates. In this work, we demonstrate an improvement in SCR by 1 order of magnitude from ~10^-6 Ω∙cm² to 10^-7 Ω∙cm² through the integration of an ultra-thin ITO interlayer. Barrier height (Φ_B) lowering by ~ 0.1 eV was observed at the MS interface as deposited which could have assisted in the reduction of the SCR. Titanium-based Ohmic contacts were subsequently formed at 950 °C. Various thicknesses of ITO were examined to assess their influence on the formation of ohmic contacts to n-type SiC. An SCR (ρ_c) of 6.9×10^-7 Ω∙cm² was achieved through integration of an ultra-thin conductive ITO interlayer at the MS interface.

Abstract: Temperature-dependent mechanisms and characteristics of 4H-SiC JBS rectifiers were described by theoretical and experimental results. The forward on-resistance of 4H-SiC JBS rectifier consists of several components, the drift region resistance is most sensitive to temperature than others. Comparing theoretical results with experimental data indicates that the leakage current is mainly affected by the thermionic emission, the image force barrier height lowering and tunneling. At different temperatures and reverse bias, the contribution of barrier lowering and the tunneling to leakage current is not the same. The temperature of critical point decreases with the increasing of the concentration of N_D or the reverse bias voltage V_R. Samples with the doping concentration of N_D=6.5E15cm^-3 and N_D=1E16cm^-3 were manufactured in the same process. The forward I–V-T and reverse I–V-T characteristics of the JBS samples were measured at different temperatures (300K to 523K), and temperature-dependent ideality factor, barrier height and resistance were also analyzed, which are in good agreement with simulation results.

Abstract: In this paper, we report on the performance of Ti/4H-SiC Schottky junctions, whereas the contact material is either e-beam evaporated or magnetron sputter deposited. When applying the first technique, the Schottky barrier height is lowered at room temperature by about 80 meV or by about 160 meV extracted from current/voltage and capacitance/voltage measurements, respectively. Furthermore, e-beam evaporation of the Ti contact results in an ideality factor closer to 1 when comparing structures of the same design.

Abstract: The aim of this work is to study the effect of Ge introduction during the nucleation step on the SiC growth on 4H-SiC on-axis substrate. After 10 minutes surface pretreatment at 1500°C under C₃H₈ or GeH₄, the grown 3C layer at the same temperature can switch from highly twinned (C₃H₈) to almost twin-free single domain (GeH₄). However, for too low and too high GeH₄ fluxes, the layers display a mixture of polytype. Keeping the best pretreatment but varying the growth temperature degrades the morphology and changes the polytype of the layer. Preliminary electrical results using C-AFM on the 3C-SiC layer are also presented.

Abstract: To distinguish the ultraviolet (UV) photoresponse of Ohmic and Schottky contact devices, we have fabricated symmetrical and nonsymmetrical devices by standard lithography based on a single WO₃ nanowire. For the Ohmic contact device, the photocurrent can change from 100 nA to 300 nA. Even 200 s under UV illumination, nonsaturated photocurrent can be observed, and the fall time is more than 1000 s. But for the Schottky contact device, the rise and fall time are faster than that of Ohmic device. The barrier height of Schottky device can be easily controlled through the oxygen adsorption and desorption on the junction region, which can be served as a ‘‘gate’’ that effectively tunes the conductance of the device. Therefore, the Schottky barrier plays a very important role in the rapid-response of UV photodetector.

Abstract: In this paper, the electricalcharacteristics of Ergermanideschottkyjunction werestudied for source / drain of n-typeschottky barrier Ge MOSFET.Ergermanideshowed the lowest ideality factor at RTP temperature of 600°C among the applied temperature range. When RTP temperature was increased, barrier height and work function of Ergermanidebecame similar to those of Er2Ge3. From the analysis of the leakage current, it is shown that the Poole-Frenkel barrier lowering was dominant at RTP 600°C and the influence of the Schottky barrier lowering was decreased as RTP temperature increased. The electrical characteristics of Ergermanideare very sensitive to the RTP temperature andclosely related tothe trapsites which are generated by germanidation.

Abstract: Temperature dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements were utilized to understand the transport mechanism of Pd Schottky diodes fabricated on Zn- and O-faces of ZnO. From I-V measurements, in accordance with the thermionic emission mechanism theory, it was found that the series resistance R_s and the ideality factor n were strongly temperature dependent that decreased with increasing temperature for both the faces (Zn and O-face) of ZnO revealing that the thermionic emission is not the dominant process. The barrier height ø _B(I-V) increased with increasing temperature for both faces. The measured values of ideality factor, barrier height and series resistance for Zn- and O-faces at room temperature were 4.4, 0.60 eV, 217 Ω and 2.8, 0.49 eV, 251 Ω respectively. The capacitance-voltage (C–V) measurements were used to determine the doping concentration N_d , the built-in-potential V_bi, and the barrier height ø _B(C-V). The doping concentration was found to be decreased with increasing depth. The barrier height ø _B(C-V) calculated for O-polar and Zn-polar faces decreases with increasing temperature. The values of barrier height ø _B(C-V) determined from C-V measurements were found higher than the values of barrier height ø _B(I-V). Keeping in view the calculated values of ideality factor, barrier height, and series resistance shows that O-polar face is qualitatively better than Zn-polar face.

Abstract: We investigated the effect of the metal work-function and doping concentration on the barrier height of Ni-contacts with embedded nano-particles (NPs) on 4H-SiC surfaces. Both n-type epitaxial layers with ND=1×1016 cm-3, and layers doped by phosphorous implantation to a doping concentration of ~1×1019 cm-3 are used. The barrier height is reduced with increasing doping concentration and the silver (Ag) nano-particles (R~18.5 nm) further enhances the local electric field of the electrical contacts to 4H-SiC in comparison to gold (Au) nano-particles (R~20.2 nm). In the case of ion-implanted samples, the barrier height of the fabricated SiC diode structures with embedded Ag-NPs was significantly reduced by ~0.09 eV and ~0.25 eV compared to the samples with Au-NPs and the sample without NPs, respectively.

Abstract: Rectifying behavior more than 3 orders of aligned zinc oxide (ZnO) nanorods grown on Mg_0.3Zn_0.7O thin film template using chemical bath deposition method was observed, giving a barrier height of 0.75 eV, and the ideality factor achieved was almost 6, which was analyzed using thermionic emission theory. Field emission scanning electron microscope (FESEM) images revealed that the grown ZnO was in hexagonal shape, uniformly distributed and in vertically aligned form. The crystallinity of the sample being studied using X-ray diffraction (XRD), where the highest peak was found at (002) phase, confirming that high crytallinity of ZnO was attained. The effect of metal/semiconductor junction between metal and aligned ZnO nanorods was discussed in further details.

Abstract: A novel method based on the analysis of the C-V hysteresis change with increasing charge release time is proposed. The presence of a band of deep traps was demonstrated using this method in 3C-SiC samples. The same band of deep traps was also observed using photo-electric measurements of barrier height EBS in the same samples.