A unique ballistic-electron spectroscopy technique has been employed to measure directly semiconductor-band-structure properties at a subsurface interface for the first time. Further, the method, based on scanning tunneling microscopy, enables spatially resolved carrier-transport spectroscopy of interfaces. A theoretical treatment has been developed which accurately accounts for the observed spectroscopic features.

• Received 3 August 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.2368