Thermal and electric field induced defects in InP metal-insulator-semiconductor structures

The presence of deep levels in several samples of InP metal-insulator-semiconductor (MIS) structures was studied using the deep level transient spectroscopy technique. The InP MIS structures were fabricated using three different methods of oxide formation, two of which are chemical oxides and the third is plasma-grown oxide. Defect levels ranging from (Ec−0.22) to (Ec−0.6) eV were observed in the samples. However, the levels at about (Ec−0.22) and (Ec−0.35) eV were detected only after increasing the reverse-bias voltage to −2 V at a temperature of about 390 K. This phenomenon occurred in all the samples studied, irrespective of the method of oxidation. The appearance of the peaks corresponding to the shallower traps is irreversible and may explain the performance instability commonly encountered in InP MIS-based devices.