| 摘要 |
PROBLEM TO BE SOLVED: To measure with reliability the bulk life time which can be obtained under sufficiently suppressed state of surface recombination. SOLUTION: Transparent electrodes 5 are disposed above and below a semiconductor sample W. DC power supplies 7 are connected between these transparent electrodes 5 and the sample W. The polarity and the magnitude of the voltage to be applied to the sample W can be changed by controlling with the means of a computer 8. Since the polarity and the magnitude of the application voltage being successively changed, the life time is measured by the photoconductive attenuation method to obtain the application voltage-life time relationship, it may be stated that as the life time increases, surface recombination is suppressed. Therefore, maximum value for the life time in the relationship is the internal life time of the sample. There is a specified relationship between the energy band state of the surface and the polarity of the voltage for approaching the accumulation state or the inversion state from the energy band state of the surface, and the surface energy band state of the sample can be evaluated from the specified relationship.
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