The piezoelectric semiconductor and acoustoelectronic device development in the sixties.

In the 1960s the properties of piezoelectric semiconductors, group III-V zinc-blende and group II-VI wurtzite structure, were explored for the development of acoustoelectronic (AE), devices. Bulk acoustic wave (BAW), delay lines, traveling wave amplifiers, and oscillators were developed. Although these elegant functional devices never made it into the realm of full-scale production and application, the piezoelectric semiconductor developments of the 1960s provided an exciting time for theoretical explanations and creative experimentation to explore device capabilities for electronic systems applications. Delay lines were formed from rectangular parallelepiped blocks of piezoelectric semiconductors with integral input and output transducers depleted of carriers at each end of the block. The ultrasonic traveling wave amplifier was based on the interaction of electrons under a bias field moving with a velocity faster than the piezoelectric field accompanying the acoustic traveling wave. The gain factor in a piezoelectric semiconductor under direct current bias was used to develop oscillators. The main research efforts were carried out by industrial laboratories with government funding support. This paper considers the work with piezoelectric semiconductors during the 1960s with examples from the author's own work.