(a) Derive the current-voltage characteristics of a p-n junction under ideal condition. How
do the I-V characteristics of a practical diode vary from the ideal characteristics?
(b) Explain the breakdown mechanisms in p-n junction diode
(c) Explain with necessary energy-band diagrams the formation of Schottky contact and
ohmic contact in the case of metal-semiconductor contacts.
3. (a) Obtain an expression for the intrinsic Fermi level (Ei) of a semiconductor with respect
to the conduction band edge.
Estimate the shift of Ei from the middle of the band gap ( ) g E / 2 at 300 K for InSb.
Assume that the relevant ratio of electron to hole effective mass for InSb is 0.014.
Sketch the energy-band diagram, indicating the position of the intrinsic Fermi level
with respect to the middle of the gap
(b) Explain drift and diffusion mechanisms of current flow in a semiconductor
In a region of a semiconductor, the electric field is directed from left-to-right (®)
while the carrier concentrations decrease with increasing x, i.e., from left-to-right.
Indicate the directions of flux of charge carriers (electrons and holes) due to drift and
diffusion. Also indicate the direction of flow of the corresponding current components.
(c) Obtain Ebers-Moll equations for a p-n-p bipolar junction transistor. Show that these
equations are true for any arbitrary geometry of the device