The molecular orbital diagram of a doped semiconductor is shown below. If the semiconductor is silicon, does the diagram represent n-type or p-type doping and which of the following elements could be dopant? (LO 12.9)
(a) n-type, As (b) n-type, Ga (c) p-type, As (d) p-type, Ga

Key Concepts

Doping in Semiconductors

Doping is the intentional introduction of impurities into a semiconductor to modify its electrical properties. N-type doping involves adding elements that have more valence electrons than the semiconductor, creating extra electrons. P-type doping, on the other hand, involves adding elements with fewer valence electrons, creating 'holes' or positive charge carriers. Understanding the type of doping is crucial for determining the semiconductor's conductivity and behavior.

Molecular Orbital Theory

Molecular Orbital Theory explains how atomic orbitals combine to form molecular orbitals, which can be occupied by electrons. In the context of semiconductors, the energy levels of these orbitals determine the material's electrical properties. The diagram in the question likely illustrates the filling of these orbitals, indicating whether the semiconductor is n-type or p-type based on the position of the added dopant's energy levels relative to the conduction and valence bands.

Dopant Elements

Dopant elements are specific atoms added to a semiconductor to achieve n-type or p-type characteristics. For silicon, common n-type dopants include phosphorus and arsenic, which have five valence electrons, while p-type dopants include boron and gallium, which have three valence electrons. Identifying the correct dopant is essential for tailoring the semiconductor's properties for specific applications, such as in transistors or diodes.