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EE 203. Final For k (^) B T at 300K, use 26 meV. Use material parameters from attached tables and figures from Sze.
- In Si a. (5 pts) How many equivalent conduction band valleys are there? b. (5 pts)Where are they?
- In Ge, a. (5 pts) How many equivalent conduction band valleys are there? b. (5 pts) Where are they?
- In GaAs, a. (5 pts) How many equivalent conduction band valleys are there? b. (5 pts) Where are they?
- Describe the valence band structure of semiconductors. a. (5 pts) Where does the maximum occur? b. (5 pts) Sketch the bands.
- (10 pts) Describe the process(es) by which an electron at the valence band maximum in Si could absorb a photon equal to the bandgap. Illustrate the process(es) on a sketch of the E-k diagrams.
- Consider a p-type (N (^) A = 10^18 cm -3^ ) Si / 10 nm SiO 2 / n-type Si (N (^) D = 10^18 cm -3^ ) structure at 0 bias and T=300K, i.e. a pn junction with a 10 nm oxide between the n and p regions. Using the depletion approximation as we did for the pn diode.
a. (10 pts) Sketch the charge distribution. Label maximum and minimum points.
b. (10 pts) Sketch the electric field. (εSi = 11.9 & εSiO 2 = 3.9) Label max and min points.
c. (10 pts) Sketch the electrostatic potential. Label max and min points.
d. (10 pts) Sketch the band diagram. (E (^) G SiO2 = 9 eV. Ec(Si0 2 ) – Ec(Si) = 3eV) (you will not be able to draw it to scale)
-xp 0 tox xn + tox
x
ρ
-xp 0 tox xn + tox
-xp 0 tox xn + tox
-xp 0 tox xn + tox
V
E
(g) (30 pts) Calculate the capacitance in (F/cm 2 ).
(b) Auger recombination (b.1) (10 pts) First describe what Auger recombination is and illustrate the process on a band diagram.
(b.2) (10 pts) Why does Auger recombination increase as the emitter doping increases?
(b.3) (10 pts) Now describe how Auger recombination affects the figures of merit, αT, γ, and βF, and thus device performance.
- As Si MOSFETS are scaled down 2 things occur that we described in class, drain induced barrier lowering (DIBL) and velocity saturation. Discuss how these effects alter device operation in saturation.
a. (10 pts) DIBL
b. (10 pts) Velocity saturation
