EVALUATION OF THE ELECTRON-ACOUSTIC SIGNAL GENERATION IN GAAS

The unambiguous interpretation of measurement results obtained by scan ning electron acoustic microscopy (SEAM) investigations of GaAs specim ens is often not possible since the mechanisms which cause the measura ble electron acoustic signals are not known exactly for GaAs. Therefor e the signal generation within the often used low-frequency range from f = 1 kHz to 100 kHz has been evaluated for semi-insulating, undoped and n-doped GaAs substrates in order to broaden the knowledge about th e importance of the different possible signal generation mechanisms. I t has been found that in n-doped GaAs substrate only the thermoelastic signal generation mechanism is dominant, whereas in a semi-insulating GaAs substrate an additional contribution of the piezoelectric sound generation mechanism exists.