The extension of a recently reported application of a dielectric spectroscopic technique on c-GaAs will be shown in the case of a-Si:H. This technique is based upon the application of a small signal a.c. voltage at several fixed frequencies using a Frequency Response Analyzer.
The technique is particularly useful for applications to material study where more traditional methods (i.e. DLTS) fail to apply. Thus we can probe the nature of bulk transport processes in the most resistive of materials and also study the interface between the contact and the substrate. It therefore becomes relatively simple to distinguish Schottky or blocking contacts from Ohmic or quasi-Ohmic contacts.
Typical capacitance and dielectric loss data will be presented as a function of frequency. Arrhenius plots obtained from the temperature dependence of the above parameters will show that activated processes have been observed and may be related to specific defect centres.