Development of semiconductor sensor as a use for pulsed electro-acoustic method

In this report, we study of fundamental research for a high positional resolution of pulse electro-acoustic (PEA) method. Positional resolution of PEA method depends on a pulse width of the applied pulse voltage and a traveling time of the acoustic signal through a piezo electric sensor. Our laboratory tried to develop a thin sensor using the polyvinylidene fluoride (PVDF). Consequently, we succeeded in developing a measuring device with a position resolution of ca. 2.5 μm using thin PVDF sensor which is 1 μm thick. However, since PVDF is polymer material, which is difficult to form a film thinner than under 1 μm. So, we focused on a depletion layer in semiconductor as a sensor material for further improvement of the sensor. The depletion layer is formed at the contact interface with the semiconductor and the metal. Which have space charge distribution inside, and it distribution is similar to an electric dipole. So we expect to apply the depletion layer for sensor. In this report, we tried to measure the space charge distribution of the depletion layer which is formed by contact a silicon substrate to an aluminum electrode. As a result, we succeeded in measuring the space charge distribution of depletion layer.