Site of Electron Acoustic Signal Generation from Junction of an npn Si Transistor-Chip under Bias Application

The junction between the base and collector of an npn Si transistor-chip was exposed to a microscopic field by angle lapping. Bias voltage applied to the chip was varied and examined by SEM and electron-acoustic microscopy with these results: (1) The site of electron acoustic (EA) signal generation stays unchanged under varying bias conditions. (2) The site of EA signal generation was almost the same as the position of the junction. (3) The EA and electron beam induced current signals closely correspond but are distinctly different. The mechanism of EA signal generation is suggested and discussed.