Showing papers by "Suzanne E. Mohney published in 2003"

Fabrication of Cobalt Silicide Nanowire Contacts to Silicon Nanowires

Abstract: A novel method to fabricate cobalt silicide nanowire contacts to silicon nanowires is described. Nanoporous anodized alumina membranes were used to define the wires' dimensions. Cobalt was deposited electrochemically within the pores of the membranes. On top of the cobalt, gold was deposited electrochemically to catalyze the growth of the silicon nanowires. The well-known vapor-liquid-solid mechanism was used to grow the silicon nanowires. During the growth of silicon, cobalt reacts with the growing silicon nanowire, forming cobalt silicide, and under certain conditions, all of the Au used to catalyze the growth of the silicon nanowire travels along the tip of the growing wire, away from the cobalt silicide/Si interface. We also discuss the influence of the amount of Au catalyst on the structural quality of the wires.

Design of a shallow thermally stable ohmic contact to p-type InGaSb

Abstract: Ohmic contacts to p-type InGaSb have been investigated. The factors that influence the contact resistance, thermal stability, and shallowness of the contacts are examined. The most desirable contact studied in this work employs three layers. A very thin layer of palladium is deposited on the p-InGaSb first and is found to lower the resistance at the metal/semiconductor interface. The next layer is W, which is predicted to be in thermodynamic equilibrium with InGaSb and which serves as a diffusion barrier to protect the semiconductor from the reaction with the final capping layer. The final capping layer is a 100 or 150 nm Au layer. The Au lowers the metal sheet resistance, which we have found both experimentally and through modeling to influence the contact resistance measurements, and the Au layer provides a contact surface that does not oxidize. The contact resistance of the as-deposited Pd/W/Au (5/50/145 nm) contact is 0.08 Ω mm (corresponding to a specific contact resistance of <3×10−7 Ω cm2), while t...

Condensed phase equilibria in transition metal–In–Sb systems and predictions for thermally stable contacts to InSb

Abstract: Antimonide-based compound semiconductors are promising candidates for high-frequency, low-power electronic devices as well as a variety of optoelectronic devices. To assist with the design of shallow or thermally stable contacts, we have performed thermodynamic calculations to estimate ternary phase equilibria in many of the transition metal-Ga-Sb systems. We have used the results of our calculations and a limited number of experiments to identify candidates for nonreactive elemental contacts to GaSb. Both W and Re are clearly in thermodynamic equilibrium with GaSb under the conditions considered in our study. Metal gallides and antimonides that are candidates for thermally stable contacts to GaSb are also highlighted.

Condensed phase equilibria in transition metal-Ga-Sb systems and predictions for thermally stable contacts to GaSb

Abstract: Antimonide-based compound semiconductors are promising candidates for high-frequency, low-power electronic devices as well as a variety of optoelectronic devices. To assist with the design of shallow or thermally stable contacts, we have performed thermodynamic calculations to estimate ternary phase equilibria in many of the transition metal-Ga-Sb systems. We have used the results of our calculations and a limited number of experiments to identify candidates for nonreactive elemental contacts to GaSb. Both W and Re are clearly in thermodynamic equilibrium with GaSb under the conditions considered in our study. Metal gallides and antimonides that are candidates for thermally stable contacts to GaSb are also highlighted.

Intermetallic growth between lead-free solders and palladium

Abstract: Intermetallic growth between Pd and the lead-free solders Sn-Ag and Sn-Ag-Cu has been studied. Diffusion couples were prepared by reflowing the solders on Pd and then aging the couples at 156°C, 175°C, 195°C, and 210°C. At the higher temperatures of 175°C, 195°C, and 210°C, PdSn4 made up most of the layer that grew between the solders and the Pd, although small regions of second phases were always found in the PdSn4 matrix, and it was sometimes possible to identify discontinuous regions of PdSn3 next to the Pd. The thickness of the intermetallic layer increased with the square root of time, consistent with diffusion-controlled growth. In couples annealed at 156°C, the morphology of the PdSn3 phase and growth kinetics differed depending on the composition of the solder.

Shallow ohmic contacts to p-type InAs

Abstract: A new Pd/Pt/Au ohmic contact to p-InAs provides a lower specific contact resistance as deposited (96×10−7 Ω cm2) than Ti-based ohmic contacts prepared on the same epilayer (26×10−6 Ω cm2 or higher) The effect of the metal deposition method and annealing conditions on the resistance of the contacts is also reported

High speed, low power electronics using Sb-based semiconductors

Abstract: In this paper the current status of the design,fabrication,and characterization of Sb-based HEMTs (6.05Am) and HBTs(6.2Am) in our group will be presented.

InAlAsSb/InGaSb double heterojunction bipolar transistor

Abstract: In this paper we report on the development of an npn double bipolar transistor with an InGaSb base and InAlAsSb alloys for the emitter and collector. The combination of alloys with a lattice constant of 6.2 a is illustrated. Silvaco simulation indicate that large collector currents, I/sub c/, are possible with this system at smaller base emitter voltages, V/sub BE/, than are measured in the InP based HBT. An important advantage of this system is that the conduction band offset between the InGaSb base and the InAlAsSb may be tuned over a large range while maintaining large valence band offsets that are useful for minimizing parasitic base currents.

Contacts to group III nitride semiconductor alloys

Abstract: In group III nitride semiconductor alloys, such as Al/sub x/Ga/sub 1-x/N, most contacts are very similar to those for GaN. In this presentation, we have explored a special consideration of the contact metallurgy alloy semiconductors and how interfacial reactions with metals can lead to compositional shifts in the semiconductor alloys beneath the contacts. High temperature annealing of the late transition Ni and Pd on Al/sub x/Ga/sub 1-x/N leads to compositional shift in the semiconductor immediately beneath the contact metal, as determined by X-ray photoelectron spectroscopy and scanning transmission electron microscopy. It has also been reported that a significant reduction in the resistance of ohmic contacts to n-type Al/sub x/Ga/sub 1-x/N with x>0.4 takes place using a contact metallurgy. In addition to describing these contacts, we offer a possible explanation for the advantage of using V-based contacts, developed by considering the metallurgy of contacts to the Al/sub x/Ga/sub 1-x/N semiconductor alloy.