A. Germanium is a semiconductor. If small amounts of the elements In, P, Sb, or

Question

A. Germanium is a semiconductor. If small amounts of the elements In, P, Sb, or Ga are placed into the Ge as impurities (not at the same time but in four separate instances) what types of semiconductors are manufactured in the four cases?

B. Normally, in conducting materials, we think of current as being carried by electrons as they move through a solid. In semiconductors, it is also common to talk about the current being carried by the “holes” in the valence band.

i. Explain how “holes” move through a solid material

ii. If, in a p-type semiconductor device, electric current is moving from left to right, in which direction will the holes be moving?

Explanation / Answer

n-type semiconductors: Ge is 14th group element, hence addition of 15 th group element (P or Sb) as impurity, it increase one electron in the system. these are called as n-type (negative) semiconductors.

p-type semiconductors: Ge is 14th group element, hence addition of 13 th group element (Tl or In) as impurity, it leaves one hole in the system. these are called as p-type (positive) semiconductors.

* (i) Formation of a hole allows the adjusent electron to jump into the hole. A electron jump into the hole, hole moves in oppoiste direction.

Hence in the solid material movement of electron and hole is in opposite direction.

* (ii) If electric current moves from left to right means holes also moves from left right, becuse movement of electrons is opposite to the direction of current and holes

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