Optimization of AuGe-Ni_Au ohmic contacts for GaAs MOSFETs

Abstract

GaAs-based metal-oxide-semiconductor field-effect transistors (MOSFETs) are promising devices for high-speed and high-power applications. One important factor influencing the performance of a GaAs MOSFET is the characteristics of ohmic contacts at the drain and source terminals. In this paper, AuGe-Ni-Au metal contacts fabricated on a thin (930 Å) and lightly doped (4 10 17 cm 3) n-type GaAs MOSFET channel layer were studied. The effects of controllable processing factors such as the AuGe thickness, the Ni/AuGe thickness ratio, alloy temperature, and alloy time to the characteristics of the ohmic contacts were analyzed. Contact qualities including specific contact resistance, contact uniformity, and surface morphology were optimized by controlling these processing factors. Using the optimized process conditions, a specific contact resistance of 5.6 10 6 cm 2 was achieved. The deviation of contact resistance and surface roughness were improved to 1.5% and 84 Å, respectively. Using the improved ohmic contacts, high-performance GaAs MOSFETs (2 m 100 m) with a large drain current density (350 mA/mm) and a high transconductance (90 mS/mm) were fabricated.

Influence of Nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures

“…A few measurements were also performed on samples with other AuGe thicknesses-50 and 150 nm. The motivation was to determine if the Ni-layer thickness to AuGe layer thickness ratio was influential in determining contact resistance, roughness (as suggested in some studies [16]) and magnetic properties. From the results summarized in table 3, it appears that this indeed is the case.…”

On the temperature-dependent characteristics of metamorphic heterostructure field-effect transistors with different Schottky gate metals

“…The variations in V th ( V th ) values for the devices A, B, C and D are 50, 82, 74 and 230 mV as the temperature is increased from 300 to 510 K. In particular, the V th of device D becomes relatively temperature sensitive when the temperature is increased above 420 K. This is mainly caused by the considerable degradation of thermal modulation effects and Schottky characteristics for the device D with the Ni/Au gate alloy, which increases the additional gate and substrate leakage paths. In other words, since the Ni metal is generally employed as a part of conventional drain/source electrode material, it helps the annealing of the AuGe/Au alloy to form the low-resistance Ohmic contact [15,16]. However, in this work, the Ni/Au alloy is introduced to act as a gate Schottky contact.…”

The contact and photoconductivity characteristics between Co doped amorphous carbon and GaAs: n-type low-resistivity and semi-insulated high-resistivity GaAs

“…Most of the commonly used metal electrode materials, such as Au, Ag, Pt, Al, etc are Schottky contact with GaAs [7]. For n-GaAs, Au/ AuGeNi is the most widely used ohmic contact material [8]. Ge/Pd and other materials are also tested to be ohmic contact electrodes of n-GaAs [9][10][11].…”