JPS6237532B

PURPOSE:To enable the non-breakdown measurement of the surface potential by a method wherein a semiconductor sample is irradiated with a modulated light beam, and the frequency dependance of the amplitude of obtained electric signals is obtained; thereby, the surface potential of the sample is calculated on the basis of a specific expression of relation. CONSTITUTION:A photon beam 10' emitted from a light source 6 is modulated into a specific frequency by a photo modulator 5, part of which is split by a beam splitter 7 and then converted into electric signals by a photo detector 8. This signal is used as the phase reference to the photo voltage. On the other hand, most of light comed into the semiconductor sample 2 through a clear electrode 3 after reflection on a reflection mirror 4. The generated photo voltage is detected by the electrode 3 and a sample table 1, and its amplitude and its phase are found out by a phase detection amplifier 9. Next, scanning the drive frequency with an oscillator 1 can yield the determination of the frequency dependance of the amplitude or phase of the photo voltage. Thereby, the specific attenuation of the potential difference or the amplitude is obtained, and the surface potential of the sample is calculated from this frequency on the basis of a specific expression of relation.