Surface impedance measurements on highly c-axis epitaxial Nd1+xBa2-xCu3O7 (
x = 0, 0.09 and 0.12) films grown by d.c. magnetron sputtering on LaAlO3 su
bstrates are presented. It is found that the zero temperature London penetr
ation depth correlates well with the critical temperature of the films and
with the corresponding number of carriers. The low temperature penetration
depth follows a linear T law for optimally doped Nd123 sample and a T-2 law
in Nd-rich samples. rn the case of the heavily underdoped samples (T-c < 6
0K) the T-2 law extends to temperatures higher than T-c/2. The possible rol
e of the Nd/Ba ions substitution on the penetration depth and surface resis
tance is discussed.