Papers by Keyword: Metal Contact

Abstract: Excellent tin oxide (SnO₂) ohmic and Schottky contacts are need for device utilizations and essential electrical characterization. Up to now, metal contact property studies on SnO₂ are inadequate and provide miscellaneous results. Ohmic contacts have been studied on high quality epitaxial n-type tin oxide thin films that were grown by solid state chemical vapor deposition (SSCVD). To the best of our knowledge, this is the first time that Al-Zn co-doped SnO₂ films grown by SSCVD have been reported. Non-alloyed Al/Ag, Al, and Ag contacts were characterized by current-voltage measurements. Ohmic contacts were realized using Al, Ag , and Al/Ag after an air treatment of the SnO₂ surface.

Abstract: The electrical characteristics of oxygen functionalized epitaxial graphene and Ti/Au metal contact interfaces were systematically investigated as a function of temperature. As the temperature was increased from 300 K to 673 K, the contact resistance and the sheet resistance decreased by 75% and 33%, respectively. The resistance of oxygen functionalized graphene vs temperature exhibited Arrhenius type behavior with activation energy of 38 meV. The results showed no hysteresis effects in resistance measurements over the temperatures studied here, suggesting the contact interfaces remain stable at high temperatures.

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: According to the need to make high quality X-ray or γ-ray detectors made by high resistance CdZnTe, the wire bonding technology between the Au contact layer of CdZnTe wafer and the down-lead has been studied in this paper. The influence of welding parameters and surface treatment of CdZnTe wafer on the welding quality between Au contact layer and down-lead have been discussed in detail, such as chemical and mechanical polishing technology of CdZnTe wafer before welding, thickness of the contact layer of CdZnTe wafer, welding energy, welding pressure, welding time, and etc. The results showed that the successful jointing between Au contact layer of CdZnTe and down-lead can be achieved when applying the suitable welding parameters and pretreatment technology of CdZnTe wafer. The optimized welding parameters for CdZnTe wafer were as follows: welding power 2w, welding pressure 60×10-3 kg, welding time 20ms and the power for fire ball formation 1.5w.

Abstract: In this study, the formation of Ni, Ni-rich Ni2Si and Si-rich NiSi2 ohmic contacts to n-type 4H-SiC are investigated. The Ni/n-SiC ohmic contact with resistance rc ~ 4.2×10-4 Ω cm2 is formed after annealing at 1050oC. For Ni2Si/n-SiC, the contact resistances were rc ~ 4×10-4 Ωcm2 and rc ~ 3.5×10-4 Ωcm2 after annealing at 1000 and 1050oC, respectively. The non-ohmic I-V characteristics are observed for NiSi2/n-SiC contact even after annealing at 1050oC. The features of ohmic contact formation for Ni-based metallization to 4H n-SiC are discussed.

Abstract: One challenge for the realization of electrically drive nano-photonic devices is the formation of metal contacts and passivation. In this paper, we report a novel self-aligned method suitable for the formation of the metal contact and passivation for submicron photonic devices. Two different dielectric materials with high selectivity in wet chemical etching and a wet etching of semiconductor to create an undercut are involved. The whole process is completely compatible with existing compound semiconductor process. As a demonstration of this method, the fabrication and characterization of an InGaAsP/InP submicron-ridge waveguide lasers is presented. The method is extendable to high aspect ratio-submicron ridge waveguide and other device fabrication.

Abstract: This study deals with the interfacial reactions and electrical properties of Ta/4H-SiC contacts. Tantalum thin films (~100 nm) were deposited onto SiC wafer at room temperature by argon ion beam sputtering. The samples were then heated in high vacuum at 650°C, 800°C or 950°C for 30 min. X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), Auger electron spectroscopy (AES) and current-voltage (I-V) technique were used for characterising the samples. Ohmic contact is formed in the studied samples after annealing at or above 800°C even though considerable amount of metallic Ta still exists. The reaction zone possesses a layered structure of Ta2C/Ta2C+Ta5Si3/SiC. High enough temperature is needed to provide for sufficient interface change to tailor the contact properties.

Abstract: In this work, we have investigated triple and innovative multiple stacked contacts onto ptype SiC in order to evaluate whether or not there is any improvement in morphology or specific contact resistivity. The stacked metal contacts are based on Al, Ti and Ni with the specific contact resistivity measured at a low value of 5.02×10-6'cm2 for an Al(100 nm)/Ti(100 nm)/Al(10 nm) (where a “/” indicates the deposition sequence) triple stacked metal contact. XRD microstructural analysis and SEM measurements have been carried out and it has been discovered that the contacts, which formed the compound Ti3SiC2 at the metal/SiC interface, more readily display low-resistance ohmic characteristics after a post deposition anneal. Although the same amount of Ti (100 nm in total) has been deposited closer to the metal/SiC interface, none of the multiple stacked structures displayed ohmic behaviour after a post deposition anneal.

Abstract: The Schottky barrier height (SBH) of Al, Ti, Au, and Ni contacts to n- and p-type 3C-SiC is investigated by means of I-V and C-V measurements. All metal contacts to n- (net donor concentration: 1.0 x 1016 /cm3) and p-type (net acceptor concentration: 4 x 1016 /cm3) 3C-SiC show the rectifying I-V characteristics except for Al contact to n-type 3C-SiC. Only Al contact to n-type 3C-SiC shows the ohmic characteristics. As the work function of metal is increased from 4.3 (Ti) to 5.2 (Ni) eV, SBH for n-type 3C-SiC is increased from 0.4 to 0.7 eV and SBH for p-type 3C-SiC is decreased from 2.2 to 1.8 eV. The small change of SBH for 3C-SiC may be correlated to the crystal orientation and the defects on the surface of 3C-SiC.