INVESTIGATION OF GALLIUM-ARSENIDE MULTILAYER STRUCTURES USING A TUNNELING MICROSCOPE COMBINED WITH A UHV-SEM

Analysis of semiconductor multilayers in an ultrahigh vacuum (UHV) environment is performed using a tunnelling microscope built into a UHV‐SEM with an Auger facility. The GaAs (110) surface is investigated with tunnelling spectroscopy and topography. As this cleavage plane is perpendicular to the preferential 〈001〉 growth direction, several material properties along the growth direction can be monitored with atomic resolution. The system is equipped with an interlocked preparation chamber for UHV cleavage of samples and for preparation of tunnelling tips, which subsequently are transferred into the scanning tunnelling microscope (STM). The SEM is used to select the sample area for the STM, with a resolution of 25 nm. Examples of results are the tracing of p‐n junctions in (Al)GaAs heterostructures and the valence band alignment in GaAs/AlGaAs interfaces. Typically, these results are obtained with a spatial resolution of 1.0–1.5 nm and are compared with results from conventional experiments (luminescence or C–V measurements), which pertain to much larger sample areas. Finally, we discuss recent results on cross‐sections of MBE‐grown (Al)GaAs multilayers, with atomic resolution in the epitaxial layers and in their interfaces. Copyright © 1990 John Wiley & Sons Ltd.