X-ray induced photoemission of a localized electron and its application to site-selective x-ray absorption fine structure measurement

For local structure analyses of carrier trap centers in semiconductors, site-selective x-ray absorption fine structure (XAFS) measurement, the "capacitance XAFS" method, is proposed. The concept of capacitance XAFS measurement is based on the fact that the amount of x-ray absorption of trap centers, not the bulk, may be evaluated from the capacitance change due to x-ray induced photoemission of a localized electron. In order to verify this model, characteristics of x-ray induced photoemission from defects are investigated by capacitance-voltage measurement. The temperature dependence of the photocarrier concentration in a semiconductor corresponds to that of the capacitance XAFS signal amplitude. On the other hand, no influence of the thermal excitation of defects on the capacitance XAFS signal amplitude is observed. These results indicate that the capacitance XAFS signal originates from localized electron emission via the inner-shell excitation of defect atoms, resulting in site selectivity to the trap centers. (C) 2000 American Institute of Physics. [S0021-8979(00)04220-1].