holetransport

Hole transport refers to the movement of holes, the absence of electrons in a material's valence band, which behave as positively charged charge carriers. In intrinsic or doped semiconductors, removing electrons (for example by acceptor doping) creates holes that contribute to electrical conduction. Holes drift in the direction of an applied electric field and participate in current alongside electrons, particularly in p-type materials.

Hole transport can proceed by band transport when holes occupy extended valence-band states, or by hopping when carriers are localized due to disorder, strong electron-phonon coupling, or at low temperature. Hole mobility μp characterizes how fast holes move for a given field; in many inorganic semiconductors μp is lower than electron mobility μe because of the greater effective mass of valence-band holes and scattering. For example, in silicon at room temperature μp ~ 450 cm^2/Vs, μe ~ 1500 cm^2/Vs. In organic and molecular semiconductors, hole transport often occurs by hopping between localized orbitals, yielding a wide range of mobilities from 10^-4 to 1 cm^2/Vs depending on material quality and morphology.

Measurement of hole transport commonly uses Hall effect to extract Hall mobility and carrier concentration, while time-of-flight and transient photoconductivity experiments probe mobility in materials with poor contacts or short-lived carriers. Transport is influenced by temperature, phonon scattering, impurities, defects, and trap states; reducing traps and crystallizing order can improve hole mobility.

Hole transport is central to p-type devices such as diodes and transistors, as well as hole-transport layers in light-emitting diodes and solar cells, where matching hole mobility to electron mobility and minimizing recombination are important design considerations.