Shown in Fig. 5 is an SIMS profile of Al and Zn for a
film deposited by PECVD with CO2 using 20mTorr of
diethylzinc and 224 1C. This film has an average resistivity
of 3:3 102 Ocm. The resistivity in the sputtered region is
1:2 102 Ocm. This figure shows that the Al concentration
peaks near the surface of the film at 1:7 1021 cm3.
This value exceeds the theoretical maximum in carrier
concentration of1:5 1021 cm3 [14]. The average concentration
throughout the 1350-nm-thick film is approximately
5:4 1020 cm3. Based on the resistivity measured
for the Al-doped ZnO film, it is estimated that less than
10% of the aluminum atoms are electrically active. Since
the SIMS measurement was made at only one position on
the sample, no conclusion can be drawn about the
distribution of aluminum across the wafer