Ohmic Contacts to implanted GaN

Ohmic contacts with low resistivity values to Si implanted GaN have been performed using a metal combination of Ti/Al. Different protection caps have been used during post-implantation annealing and their influences to the specific contact resistivity (rho
_c
) have been investigated. After the metal alloying, noticeable differences have been observed between the protected sample with SiO
₂
and unprotected sample during the post-implantation annealing. The unprotected sample has shown lower values of rho
_c
but with very low reproducibility, while, by contrast, the use of SiO
₂
cap has revealed the achievement of a low rho
_c
around 10
^-5
Omega.cm
²
with very good uniformity. Based on the results obtained from electrical measurements, XRD (X-ray diffraction) analysis, AFM (atomic force microscopy) and SEM (scanning electron microscopy) observations, we discuss the mechanism for the uniformity in rho
_c
.