Capacitance-voltage characteristics of organic insulating films on semiconductors.

摘要

The purpose of this research was to examine the applicability of organic thin films as electrical insulators in metal-insulator-semiconductor (MIS) devices. Thermal evaporation in a vacuum has been used to deposit organic insulating films and aluminum contacts to form MIS devices.;Organic stearic acid insulating films may provide a good substitute dielectric medium for MIS technology. Several types of measurements are used to examine the properties of stearic acid films.;Capacitance versus Voltage (C-V) measurements of the stearic acid films in MIS devices at 1MHz display close to ideal C-V characteristics for a silicon substrate. In a compound semiconductor with a gallium arsenide (GaAs) substrate, the stearic acid films did not show ideal C-V characteristics. This lack of ideal C-V characteristics in GaAs is attributed to the absence of ohmic contact with the semiconductor. The ohmic contact problem can be partially overcome for n-type GaAs by adding an aluminum coating on the back of a semiconductor. The p-type GaAs showed no improvement.;The 1MHz C-V measurements of the stearic acid films in MIS devices after subjecting them to temperature stress are used to determine surface defect densities at the semiconductor/insulator interface.;Variable frequency C-V measurements in MIS devices display anomalous frequency dispersion in the negative bias voltage region for p-type semiconductor substrates and in the positive bias voltage for n-type semiconductor substrates. This can be attributed to the formation of surface states at the semiconductor/stearic acid insulator boundary. Finally, conclusions are drawn as to the applicability of this type of organic material as an insulator and in compound semiconductors as a substrate in MIS devices.