Abstract

Photoconductively gated ultrafast scanning tunneling microscopes (USTM’s) have been demonstrated on transmission lines.¹² We show its applicability on semiconductor structures and use the USTM to resolve field transients on semiconductor layers. A 100-fs laser pump beam generates carriers in the semiconductor layer while the probe beam gates the signal picked up by the tunneling tip in a photoconductive switch. The sample consists of a 1.5-μm thick layer of MBE grown GaAs layer grown at either standard or low substrate temperature (LT GaAs). The GaAs layer is placed on a transparent substrate with a semitransparent Au-layer by epitaxial lift-off. The transparent substrate allows for illumination from the back (Au) side as well as from the front (tip) side.

© 1998 IEEE