Mean energy required to produce an electron-hole pair in silicon for photons of energies between 50 and 1500 eV

The photon energy dependence of the mean energy W required to produce an electron-hole pair in silicon for photons with energies between 50 and 1500 eV was determined from the spectral responsivity of selected silicon photodiodes. The spectral responsivity was measured with a relative uncertainty of less than 0.3% using monochromatized synchrotron radiation whose radiant power was measured with a cryogenic electrical substitution radiometer. In order to deduce W from the spectral responsivity of photodiodes with a relative uncertainty of about l%, a method for the calculation of photon and electron escape losses from silicon photodiodes was developed and the model for the charge carrier recombination losses was improved. In contrast to recent theoretical and experimental results, a constant value W=(3.66+/-0.03) eV was obtained in the photon energy range from 50 to 1500 eV. The present experimental results are confirmed by calculation of the pair creation energy in silicon from data from the literature for the relevant material properties. The difference from previous theoretical work is due to different assumptions about the influence of the band structure of silicon. (C) 1998 American Institute of Physics. [S0021-8979(98)01817-9].