 
pn junctions
Reading: Sze chapter 4 or Singh sections 5.15.9 or Thuselt 3.1  3.4
For the exam:
 Know the depletion approximation and how the the charge distribution, electric field, the potential, and the width of the depletion layer are calculated in this approximation. Known what the builtin voltage $V_{bi}$is and why it appears. See: Abrupt junctions.
 Be able to draw a band diagram (conduction band, valence band, Fermi energy) of a pnjunction in forward or reverse bias.
 Know how the width of the depletion layer and the doping can be measured using a Capacitance  Voltage (CV) measurement.
 Be able to explain how a pn junction can be used as a variable capacitor.
 Be able to explain carrier generation and recombination in a pndiode. Know the equations for drift ($\vec{j}_{n,drift}= ne\mu_n\vec{E}$, $\vec{j}_{p,drift}= pe\mu_p\vec{E}$) and diffusion ($\vec{j}_{n,diff}= eD_n\nabla n$, $\vec{j}_{p,diff}= eD_p\nabla p$) of electrons and holes.
 The diode equation $I=I_0(\exp(eV/k_BT)1)$ describes the diffusion current in a pnjunction. Know how to determine the electron and hole diffusion currents that lead to the diode euquation. Know why a nonideality factor sometimes has to be included in this equation.
 Be able to explain what happens to the depletion widths, the drift and diffusion currents, and the minority carrier concentrations for forward and reverse bias.
 Be able to describe avalanche breakdown and Zener tunneling.
Selfassessment questions on pnjunctions
Problems
1. The depletion approximation for a pn junction
2. pn junction
3. Depletion width in reverse bias
