Analysis of the p-n Junction June 30, 2015 Chapter VI

Calculation of Carrier density and Current Densities Currents and carrier densities in the neutral regions

Depletion layer width with or without applied bias

With applied bias

Same as Eq (4-48a) in Sze V

Light passing through a semi-transparent medium follows Bouguer’s (Bouguer-Lambert’s, or Beer’s) Law Where b is the light energy passing through the medium per unit area, and is the absorption per unit volume.

Currents and carrier densities in the space charge region

Total Current Density Current from p to n is positive and is opposite to the convention.

No light and no applied bias

No light but with forward bias

P-n Junction under Illumination Short circuit current: V=0

Under short circuit condition: V=0 In the depletion region, E Fn = E Fp

Medium has a higher absorption coefficient for short wavelength light

Penetration depth in a semi- transparent medium Solution from Electro-magnetic (Maxwell) wave equation in a semi-transparent medium: where k is the extinction coefficient for the medium. For light intensity, the decay of light should follow

continue Penetration depth of light in a semi-transparent medium can be found when

When x p exceeds L n, emitter is too thick. Part of the region becomes dead layer.

Open circuit voltage J m,o is similar to J R in Eq 4-59 in Sze. for N A >> N D

PV cell with a resistive load

Due to reduced band gap at higher T