M.Sc Thesis

M.Sc StudentMehari Shlomo
SubjectNi-InGaAs Alloy as Silicide-Like Metallization of InGaAs
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Dan Ritter
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


This research thesis describes a study of the Ni-InGaAs alloy as silicide-like metallization of InGaAs. Several aspects of the Ni-InGaAs properties were investigated within this research. First, structural properties were investigated using TEM, XRD and SIMS. It was found that Ni-InGaAs alloy is homogeneous and crystalline with an abrupt interface to the remaining InGaAs layer underneath. X-ray diffraction patterns revealed the formation of the Ni-InGaAs phase.

Second aspect of the study was focused on the Schottky contact of the Ni-InGaAs alloy to n-InGaAs layer. Temperature dependency of the current voltage relationship of the Ni-InGaAs/n-InGaAs Schottky diodes was examined. A nearly ideal behavior was obtained, indicating that the interface between Ni-InGaAs and InGaAs was clean and oxide free, as expected for silicide-like contacts. The Arrhenius plot across wide range of temperatures was linear, and as a result an accurate evaluation of SBH was obtained. The extracted barrier height was 0.239?0.01 eV, a considerably larger value than reported before which may limit the performance of transistors having Ni-InGaAs drain and source. However, the nearly ideal interface may be useful for obtaining better ohmic contacts.

The ohmic properties of the Ni-InGaAs alloy to the p-type base layer of InGaAs/InP HBT were investigated. The contact resistivity of the Ni-InGaAs alloy to p-InGaAs layer was evaluated using two types of TLM test structures processed on semi-insulating InP substrate. It was found that the resistivity of Ni-InGaAs alloy is 64 ?Ωcm and the specific contact resistivity of Ni-InGaAs to p-InGaAs is 6.2?1.23 Ω?m2 which is order of magnitude lower than TLM measurements of conventional Pt based contacts.

The influence of Ni-InGaAs alloy formation on junction performance was investigated using large area p-InGaAs/n-InP diodes. Electrical measurements and TEM analysis of p-InGaAs/n-InP diodes with different thicknesses of Ni revealed that the junction performance is degraded with the increase of Ni thickness deposited.

Evaluation of contact resistivity was done using direct measurements of small area p-InGaAs/n-InP diodes using conventional HBT geometry structure. The evaluation was done due to the errors of TLM for contact resistivities less than 10 Ω?m2. It was found that the specific contact resistivity of conventional Pt based contacts and Ni-InGaAs based contacts is less than 1 Ω?m2 as evaluated on 100 nm thick p-InGaAs layer. If conventional Pt based contacts or Ni-InGaAs contacts are employed for thin p-InGaAs layer sinking of Pt or Ni penetration through the p-InGaAs layer degrades the junction performance by forming Schottky contact to the InP layer.