Meaning
Charge conduction governed by space charge limitations defines the current-voltage relationship in highly insulating materials under unipolar carrier injection. In organic semiconductor testing and thin dielectric films, Mott Gurney kinetics describes the square-law dependence of current on voltage when the injected charge density exceeds the intrinsic background carrier concentration. This behavior is fundamental to analyzing carrier mobility in low-conductivity electronic materials.
Carrier Transport
High voltage application injects a substantial number of carriers that accumulate near the injecting electrode, forming a localized space charge. This localized charge alters the internal electric field distribution, and Mott Gurney kinetics models the resulting current limit when transport is purely drift-dominated. This model assumes that traps are either filled or absent within the bandgap.
Current Density
Current scales quadratically with voltage and inversely with the cube of the sample thickness in accordance with this electrostatic transport theory. Physical measurements of organic thin-film transistors rely on this relationship to calculate carrier mobility from experimental current-voltage sweeps. Deviations from this behavior suggest the presence of a high density of deep trap states.
Voltage Dependence
Transition from ohmic conduction to the space-charge-limited regime occurs at a specific transition voltage. This transition voltage is proportional to the concentration of free carriers in the film.
