Formula:
The saturation current (Is) in a PN junction diode is fundamentally described by the following relationships:
Is = A × q × ( (Dp / Lp × pn0) + (Dn / Ln × np0) )
Where equilibrium minority carrier concentrations are:
pn0 = ni2 / ND
np0 = ni2 / NA
And the intrinsic carrier concentration squared (ni2) is temperature-dependent:
ni2 = B × TK3 × e(-Eg / (keV × TK))
Variables Explained:
Is: Saturation Current (Amperes)A: Diode Cross-sectional Area (cm2)q: Elementary Charge (1.602 × 10-19 C)Dp: Hole Diffusion Coefficient (cm2/s)Lp: Hole Diffusion Length (cm)ND: Donor Concentration (cm-3)Dn: Electron Diffusion Coefficient (cm2/s)Ln: Electron Diffusion Length (cm)NA: Acceptor Concentration (cm-3)pn0: Equilibrium Hole Concentration in N-side (cm-3)np0: Equilibrium Electron Concentration in P-side (cm-3)ni: Intrinsic Carrier Concentration (cm-3)B: Material-specific Constant (cm-6 K-3)TK: Temperature in Kelvin (TC + 273.15)Eg: Band Gap Energy (eV)keV: Boltzmann Constant (8.617 × 10-5 eV/K)