P-Type Semiconductor

When a trivalent impurity (like Boron, Aluminum etc.) is added to an intrinsic or pure semiconductor (silicon or germanium), it is said to be a p-type semiconductor. Trivalent impurities such as boron (B), gallium (Ga), indium (In), aluminum (Al) etc. are called acceptor impurity. Ordinary semiconductors are made of materials that do not conduct (or carry) an electric current very well but are not highly resistant to doing so either, metalloids, such as Silicon (Si), Germanium (Ge), Arsenic (As), and a few other element commonly used for the main body of semiconductors. They fall halfway between conductors and insulators and so are called semiconductors. For an electric current to flow, electrons have to move through a material. In order to move, there must be an electron hole in the material for the electron to move into. A p-type semiconductor has more holes than electrons. This allows the current to flow along the material from hole to hole but only in one direction.

Semiconductors are most often made from silicon. Silicon is an element with four electrons in its outer shell. To make a p-type semiconductor, extra materials like boron or aluminum are added to the silicon. These materials have only three electrons in their outer shell. When the extra material replaces some of the silicon it leaves a hole where the fourth electron would have been if the semiconductor was pure silicon.

P-type semiconductors are doped with acceptors since they can accept electrons while N-type semiconductors are doped with donors since they 'donate' the free electrons. PN junctions such as diodes rely on the diffusion of electrons from N-type semiconductors to P-type semiconductors to function, only permitting current in one direction.

P-type semiconductors are made by doping the pure semiconductor material. The amount of impurity added is very small compared to the amount of semiconductor. The exact character of the semiconductor can be changed by varying the amount of dopant that is added. In p-type semiconductors the number of holes is much higher than that of thermally generated electrons.

• Semiconductor
• N-type semiconductor

• The Doping of Semiconductors - Hyperphysics
• PN Junction Theory - Electronics Tutorials