The Reverse Bias Region

The reverse bias region of operation is entered while the diode voltage is made -ve. The past equation show that if v is -ve and a little times larger than V_T in magnitude the exponential term will be negligibly small as compare to unity & diode current will  becomes

                                                            i = -I_s

i.e., the current in the reverse direction is constant & equivalent to I_s. This constancy is the cause behind the saturation current.

A good part of the reverse current is because of the leakage effect.

The leakage currents are proportional to the junction area, only as I_s. It's based on temperature is yet, different from I_s.