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6.19: Band Gaps and Conduction and Valence bands

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    As shown in Figure 6.21.1, if the Fermi energy separates two bands of allowed electron states, the upper band is empty and the lower band is full. The energy difference between the top of the filled band and the bottom of the empty band is known as the band gap. Empty bands that lie above the Fermi energy are known as conduction bands. Filled bands that lie below the Fermi energy are known as valence bands. In this class, we have mostly considered charge transport through the conduction band. Charge may also move through vacancies in the normally full valence band. These vacancies are known as holes. Holes are effectively positively charged because the semiconductor no longer has its full complement of electrons. Consequently, a MOSFET that conducts through its valence band is known as pchannel MOSFET. It requires a negative \(V_{GS}\) to turn on.

    Screenshot 2021-05-26 at 13.59.51.png
    Figure \(\PageIndex{1}\): The energy difference between the top of a filled (valence) band and the bottom of an empty (conduction) band is known as the band gap.

    6.19: Band Gaps and Conduction and Valence bands is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.