Dielectric Relaxation and Its Effect on the Isothermal Electrical Characteristics of Defect Insulators
The effect is considered of dielectric relaxation on the I-V characteristics of metal-insulator-metal (MIM) systems when blocking contacts exist at the insulator surfaces. It is shown that the dielectric relaxation time (DRT) has a strong influence on the dc electrical properties of the insulator. If the DRT is short (<10-3 sec), then the conduction mechanism measured is a steady-state process for increasing voltage bias, but for decreasing voltage bias the system exists in a quasisteady state if the insulator has good blocking contacts; this being the case, the J-V characteristics will manifest hysteresis. If the DRT is long (>104 sec), the conduction mechanism involved is essentially a non-steady-state process. Also, the DRT is a very sensitive function of temperature; it increases with decreasing temperature. Thus, a conduction mechanism that is a steady-state process at room temperature, may well be a non-steady-state process at low temperatures. In the MIM system under consideration, the steady-state conduction process (short DRT) is shown to be an electrode-limited process, while the non-steady-state measurement is a bulk-limited process, even though blocking contacts exist on the insulator surfaces. If the DRT is moderate (~= 102 sec), a time-dependent relaxation current is observed, from which the trap density, amongst other insulator properties, can be determined. Other non-steady-state processes, such as current reversal (i.e., current flowing in the opposite direction to conventional current) are described.