Laser annealed Ta/Ge and Ni/Ge ohmic contacts to GaAs

Refractory metal ohmic contacts to n-type GaAs have been developed using epitaxial Ge films and pulsed laser annealing. Laser annealing was carried out with a 22 ns pulse from a Q-switched ruby laser operating in the TEM
00
mode. The specific contact resistivity of the contacts Ta/Ge and Ni/Ge on 2 × 10
¹⁷
cm
^-3
dopes GaAs exhibited sharp minima as a function of laser energy density at 1 × 10
^-6
Ω-cm
²
and 2 × 10
^-6
Ω-cm
²
, respectively, which occurred near the melting point of the layered contacts. Auger electron sputter profiles revealed Ge migration into the GaAs surface after laser annealing at sufficient energy density to form ohmic contact. The contacts have applications to high temperature devices and to devices which experience high channel or contact temperatures, such as power FETs and TEDs.