Application of Saw Delay Line Attenuation and Transverse Acoustoelectric Voltage for Determination of Semiconductor Surface Properties.

摘要

The study of the semiconductor surfaces, using acoustoelectric voltage and delay line attenuation as a tool has been recently reported. Acoustoelectric voltage is the result of non-linear interaction between semiconductor space charge carriers and surface acoustic waves (SAW) in a semiconductor on LiNbO3 convolver structure. The study is based on the time dependent change of attenuation constant of the delay line and the transient phenomena of acoustoelectric voltage. In this paper we report the change in attenuation constant observed by mixing two rf pulses, one of small amplitude with long duration and other of large amplitude and short duration. Acoustoelectric voltage generated by the short rf pulse induces surface changes which are captured by semiconductor surface traps after a certain time, and as a result the attenuation constant of the long rf pulse changes during this time. From this, information about the density and type of traps of semiconductor surface can be obtained. The surface of the semiconductor was illuminated through the LiNbO3 in order to change the surface conditions. Experiments have been performed using silicon of different type and surface properties. This method has the advantage of being absolutely contactless and very simple. (Author)