Echo phenomena in piezoelectric crystals

We report an extensive set of experimental measurements on electric-field echoes in insulating and semi-insulating crystals. Previously suggested mechanisms cannot explain the results. In particular, three-pulse echoes with decay times T1 of several hours have been observed at low temperatures in semi-insulating II-VI compounds. We propose a mechanism based upon the redistribution of trapped electronic space charge. © 1973 The American Physical Society.