Microstructure studies of AuNiGe Ohmic contacts to n-type GaAs

Abstract

Transmission electron microscopy studies of the microstructure of AuNiGe ohmic contact to n-type GaAs Microstructure analysis and contact resistance measurements of alloyed AuNiGe contacts to GaAs were performed to assist in the development of low resistance Ohmic contacts for metalsemiconductor field-effect transistor (MESFET) devices. The contact metals were prepared by sequential deposition of 100 nm of Au-27 at. % Ge, 35 nm Ni, and 50 nm Au onto sputter-cleaned GaAs wafers in which conducting channels were formed by Si doping to a level of about 1 X 10 18 cm -3. The contact resistances were determined by the transmission line method. Analysis of the substrate and the film microstructure was carried out by x-ray diffraction, Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy (XPS). A strong correlation between the contact resistance and the film microstructure was observed. Low resistances were observed when NiAs compounds containing Ge were in contact with GaAs and the {3-AuGa phase was concentrated near the top of the contact. High resistances were measured when free Au, the a-AuGa phase, or a NiGe compound were present. The temperature dependence of the contact resistance and the kinetics of compound formation were found to be influenced by the deposition sequence. Deposition of 5 nm Ni as a first layer significantly enhanced the formation of the NiAs compounds containing Ge, resulting in low contact resistance at a lower alloying temperature. However, a further increase in the thickness of the first Ni layer to 10

The Achievement of Low Contact Resistance to Indium Phosphide: the Roles of Ni, Au, Ge, and Combinations Thereof

“…Although it has been fLrmly established that Ge in the Au-Ge-Ni system plays a crucial role in lowering Pc to very low values on GaAs [3,4], we have found that its presence is not necessary to achieve very low Pc values on InP. Our investigations of Ni, Au, Au-Ni, and Au-Ge-Ni contact systems on InP have resulted in several findings.…”

Ohmic contacts properties of Ni/Ag metallization scheme on p-type GaN

“…The surface oxide is known to increase effective Schottky barrier height and to deteriorate the metal/GaN interface, leading to the degradation of ohmic contacts. Historically, the Ni metallization was cited as a wetting agent [28], but it was later deduced that Ni has other roles including reduction of the surface oxides and reacting with GaN at low temperatures to form binary and ternary compounds that may be electrically important.…”

Effect of thermal annealing on the Ir/Ag contact to p-type GaN

“…The surface oxide is known to increase effective Schottky barrier height and to deteriorate the metal/GaN interface, leading to the degradation of ohmic contacts. Historically, the Ir metallization was cited as a wetting agent [29], but it was later deduced that Ir has other roles including reduction of the surface oxides and reacting with GaN at low temperatures to form binary and ternary compounds that may be electrically important.…”