Study on electrical properties of metal/GaSb junctions using metal-GaSb alloys

Study on electrical properties of metal/GaSb junctions using metal-GaSb alloys
Koichi NishiMasafumi Yokoyama김상현Haruki YokoyamaMitsuru TakenakaShinichi Takagi
Issue Date
Journal of applied physics
VOL 115, NO 3, 034515-1-034515-7
We study the metal-GaSb alloy formation, the structural properties and the electrical characteristics of the metal-alloy/GaSb diodes by employing metal materials such as Ni, Pd, Co, Ti, Al, and Ta, in order to clarify metals suitable for GaSb p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) as metal-GaSb alloy source/drain (S/D). It is found that Ni, Pd, Co, and Ti can form alloy with GaSb by rapid thermal annealing at 250, 250, 350, and 450 °C, respectively. The Ni-GaSb and Pd-GaSb alloy formation temperature of 250 °C is lower than the conventional dopant activation annealing for ion implantation, which enable us to lower the process temperature. The alloy layers show lower sheet resistance (R Sheet) than that of p +-GaSb layer formed by ion implantation and activation annealing. We also study the electrical characteristics of the metal-alloy/GaSb junctions. The alloy/n-GaSb contact has large Schottky barrier height (ϕ B) for electrons, ∼0.6 eV, and low ϕ B for holes, ∼0.2 eV, which enable us to realize high on/off ratio in pMOSFETs. We have found that the Ni-GaSb/GaSb Schottky junction shows the best electrical characteristics with ideal factor (n) of 1.1 and on-current/off-current ratio (I on/I off) of ∼104 among the metal-GaSb alloy/GaSb junctions evaluated in the present study. These electrical properties are also superior to those of a p + -n diode fabricated by Be ion implantation with activation annealing at 350 °C. As a result, the Ni-GaSb alloy can be regarded as one of the best materials to realize metal S/D in GaSb pMOSFETs.
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