PX262 - L1 - introduction to semiconductors

• exploring why some materials show such a drastic bias to the direction of emf

• for $T\ne 0$ K, the fermi-dirac function:

• such that:

where, $N$ is the number of electrons, and $\mu (\simeq E_F\simeq E_V+\mathrm{\Delta }/2)$ is the chemical potential

• each atom in group IV elements: C, Si, Ge, has core of electrons, tightly bound to the nuclei and four loosely bound valence electrons

• considering Si: $\mathrm{\Delta }=1.1$ eV $=E_C=E_V$
• at $T=300$ K, $\mu \simeq E_F=E_V+\mathrm{\Delta }/2$

• this is very small
• therefore, semiconductors need to be doped to conduct easily, ie. add impurities