Transition from Electrode-Limited to Bulk-Limited Conduction Processes in Metal-Insulator-Metal Systems

If a blocking contact exists at a metal-semiconductor interface, the conduction process is electrode-limited and will normally remain so, that is, it will not become bulk-limited with increasing applied voltage unless the semiconductor is inordinately thick. It is shown, however, that in an insulator containing a high density of traps and donors, such as one might expect in evaporated insulating films, the conduction process can change from being electrode-limited to being bulk-limited. This process results at low voltages in a very steep $I-V$ characteristic which is essentially thickness-independent (electrode-limited), and at high voltages in a law $I\propto \exp \beta V^{\frac{1}{2}}$ which is thickness-dependent (bulk-limited). The results are shown to be in agreement with existing experimental data.