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Why can n-channel MOS transistors operate faster than p-channel MOS transistors?

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NMOS transistorNegative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors. — transistor NMOS transistor
Negative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors.

The operating frequency of a metal-oxide-semiconductor (MOS) transistor is largely determined by the speed at which charge carriers—either electrons or holes—can drift through the semiconductor material divided by the distance between the source and the drain.1

In an n-channel MOS (NMOS) transistor, the primary charge carriers are electrons, whereas in a p-channel MOS (PMOS) transistor, the primary charge carriers are holes. Because electrons possess mobilities through silicon that are approximately three times higher than those of holes, NMOS transistors are capable of operating at substantially higher frequencies than PMOS transistors.1

While holes can carry current, they generally move more slowly than electrons because they function within the more tightly bound valence band of the semiconductor material rather than the conduction band. Consequently, the superior mobility of electrons allows NMOS devices to achieve faster switching and higher operating speeds compared to their PMOS counterparts.21