It was pointed out that superconductor tunnel junctions, when used as tunable sources of quasi-monochromatic acoustic phonons and as broad-band phonon detectors, permitted the use of a sensitive spectroscopic technique over almost the entire acoustic band. This was suitable for the investigation of defects in semiconductors. The method offered high sensitivity, good resolution and wide range of tunability for the investigation of various types of defect in Si and Ge. The technique was also applicable to III-V compounds; especially GaAs.

K.Lassmann: Materials Science Forum, 1995, 196-201, 1563-70