Contacts on GalnAs

The specific contact resistance ρ
c
of Ni/Au-Ge/Ni and Ni/Au-Sn/Ni layers on n-GaInAs and Ni/Au-Mg/Ni and Ni/Au-Zu/Ni on p-GaInAs are measured for different alloying temperatures and times using an extended transmission line model. Specific contact resistances of 4.10
^-8
Ω cm
²
for Ni/Au-Sn/Ni on n-GaInAs (n = 10
¹⁸
cm
^-3
) and 2.10
^-5
Ω. cm
²
for Ni/Au-Zn/Ni on p-GaInAs (p = 10
¹⁸
cm
^-3
) are obtained. After deposition at room temperature, the barrier height of the metal-n-GaInAs system was determined to be 0.16 eV, decreasing below 20 meV after heat treatment. Interdiffusion of metal and semiconductor was investigated by SIMS/Auger measurements. At alloying temperature of 300°C the contacts show fast diffusion of Au relative to the dopants, effecting an increase of the specific contact resistance.