Question

Homework 5 Consider a semiconductor characterized by electronic affinity ez and work function ec This semiconductor makes contact with a metal described by a work function e p type with N a- Explain the nature and the modification appeared during this contact. Particularly, in the side of semiconductor. b- Represent an explicative scheme of band structure for a forward bias of heterojunction. c-Establish the expression of electric field and potential. Given V(0) = 0 The built in potential is noted V d- Establish the expression of the depleted zone width W with N&density of donors. a- By using an analogical approach between n type semiconductor and p type semiconductor, establish the expression of the capacitor (C) of this diode. b-Prove that the variation of 3 as a function of V, is a linear curve. We note V, the applied

Answer 1

1) a) In p-type semiconductors which are created by doping an intrinsic semiconductor with an electron acceptor element during manufacture. The p-type refers to the positive charge or holes. The p-type semiconductors have a larger hole concentration than electron concentration. In this, the holes and electrons are the majority carriers and minority carriers respectively. For p-type semiconductors the Fermi level is below the intrinsic Fermi level and lies closer to the valence band than the conduction band.

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b)

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d)

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2) a) To calculate the junction capacitance of a Schottky Diode, the capacitance between the Schottky metal and the semiconductor, we have to calculate the number of charged particles transferred to the metal. Well this can be done using simple geometry, the depletion region width multiplied by the anode size and also the charge density resulting to the total amount of charge, the only depletion region width is unknown, as the charge density is equal to the doping density of the semiconductor and the junction area is defined in the fabrication process.

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b)

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