Dielectric constant: Si = 11.9 ; SiO2 =3.9. Bandgap: Si = 1.12 eV ; GaAs = 1.42 eV. 1. A silicon sample has a doping profile with donors ND = NO exp(-mx). If ND >>ni, find the expression for the built-in electric field at equilibrium. (20%)

4. For heterojunctions in the GaAs-AlGaAs system, the direct bandgap difference is accommodated approximately in the conduction band and in the valence band. The bandgap of AlGaAs is 1.85 eV if Al composition is 0.3. Draw the band diagrams of two heterojunctions: (a)As on n-GaAs (b)As on n-GaAs (20%)

Dielectric constant: Si = 11.9 ; SiO₂ =3.9. Bandgap: Si = 1.12 eV ; GaAs = 1.42 eV.
1. A silicon sample has a doping profile with donors N_D = N_O exp(-mx). If N_D>>n_i, find the expression for the built-in electric field at equilibrium. (20%)

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