On the linearity and parabolicity of the PIN dark IV: the effect of series resistance

The article provides simple analytical expressions for calculating the exact current-voltage (IV) characteristic of a PIN diode. Focus is on the differences between the PIN and the PN IVs. The I-layer width is assumed to be much greater than the material's intrinsic Debye length. Truthfulness of all derived equations is verified by comparing with numerical simulations. As expected, the IV gets limited by the device's series resistance (Rs) at high forward bias. However, whether the PIN IV is linear, or parabolic (or in between) depends on which of the P, I, and/or N layer(s) dominate(s) the Rs. A transition from linear to parabolic behavior is observed as the width of the intrinsic layer is increased. Equations for the knee voltages and series resistances are also analytically derived, and are corroborated with numerical simulations.