Two p+-n abrupt junction diodes are made from silicon and are identical except that the donor levels in the 2 diodes are ND_1=10^15 and ND_2 = 1x10^17 cm-3. Sketch on one set of axes the I-V characteristics of the diodes for operation at room temperature. Label each curve. Also sketch on the same (or similar) axes the I-V curves for the diodes at - 100 C. Repeat for 100 C. As the temperature is lowered much further below - 100C, what phenomena would limit the operation of the diodes?

Don't I need to know the saturation current for each of the two diodes? How do I find this based on the donor levels? Do I need to find the built-in voltage as well? I had intended to utilize the diode equation:

I = I_0(exp(eV/kT)-1), but I am not sure how to find the saturation current (I_0) with the dopant concentrations. If you can guide me in the right direction on finding I_0 I can do the rest on my own.