Drift Mobility Measurements

Abstract

Measurements of drift mobility have been made by observing the transit time t of a pulse of charge carriers over the distance x between the point of photoinjection and a ``point of detection.'' The detector point may be a reverse biased junction, a constriction in the cross-sectional area, a point contact electrode, or other electrically indicating semiconductor construction. The arrival of the injected pulse at the detector results in a relatively large change in the conductance of the specimen. A signal taken from a load resistor in series with the sample is observed on the CRO. The time t is plotted against x. The reciprocal slope of the curve gives pulse drift velocity which when divided by the field strength E(x) gives the corresponding mobility μ(x). For a junction, electron mobility is determined by injection in the p region; hole mobility is determined by injection in the n region.