Electric field dependence of hydrogen neutralization of shallow-acceptor impurities in single-crystal silicon

Abstract

An electric field applied to p-type single-crystal silicon during hydrogenation dramatically affects the neutralization of shallow-acceptor impurities (e.g., boron). This is demonstrated with capacitance-voltage and secondary-ion mass spectrometry measurements on n+-p junction diodes that were reverse biased during exposure to monatomic deuterium at elevated temperatures. The results reveal that there is no neutralization within the field-induced space-charge layer, which extends from the metallurgical p-n junction into the p-type material. Rather, deuterium-boron pairing occurs in the electrically neutral material beginning at the edge of the depletion layer. Consequently, the distribution of deuterium (hydrogen) is also altered by the applied field. The effect of an electric field on hydrogen-boron pairing in p-type silicon is discussed in terms of the role of free holes in the chemical reaction and possible charge states of the diffusing hydrogen atoms.