The relationship is:
R = R∞eT0/T
where R∞ is the value that the resistance (R) approaches as the temperature (T) gets very large and depends
on the sample, T0 is a characteristic temperature for the semiconductor. The quantity T0 can be different for
each type of semiconductor material (silicon, germanium, etc.). The above relationship for the
semiconductor only applies if the temperature is expressed in Kelvin. (TKelvin = TCelsius+273)
[copied from google... and thanx.. i too din know this :)]