Electric-field-enhanced electron emission from isolated sulfur and selenium donors in silicon

The electric field effect on the thermal electron emission of isolated sulfur and selenium centers was studied in silicon. Various degrees of field dependences were observed for all centers except for the neutral sulfur center, which exhibited almost no field effect. Taking the measured field dependences into account it is shown that the zero-field enthalpies are in good agreement with previously measured optical binding energies. However, experimental evidence suggests that field-effect studies are not always reliable measurement techniques to identify whether the defect studied is an acceptor or a donor level.