| 摘要 |
PURPOSE:To decrease the generation of noises, by forming the length of a charge detecting element in the propagation direction of ultrasonic waves, which are propagated in a piezoelectric body, of a charge transmission element for transmitting charge carriers on a surface of a semiconductor in the length of integer times as long as the wavelength of the ultrasonic waves by means of an electric field being accompanied by the ultrasonic waves. CONSTITUTION:A portion near a surface of a semiconductor 10 is depleted by applying voltage to a conductive layer 14, and the waves 18 of electric potential are propagated in a depletion layer by applying high-frequency voltage to comblike electrodes 15, thus a small number of carriers in the depletion layer are bound by means of the modes of the waves 18 of the electric potential and transmitted in the arrow head 17 direction. Charge carriers 25 are generated by means of the irradiation of light or an injection diode 19. The carriers transmitted through an injection gate 20 are detected by means of a detecting diode 22 through a detecting gate 21. Length d in the progressive direction 17 of the waves 18 of the electric potential of the detecting diode 22 is made up in the length of integer times as long as the wavelength lambda of the waves 18 of the electric potential. Thus, noises due to piezoelectric potential are eliminated, and only carriers can be detected. |
