P. Demierry et al., DEFECTS INDUCED IN P-TYPE SILICON BY PHOTOCATHODIC CHARGING OF HYDROGEN, Journal of the Electrochemical Society, 141(6), 1994, pp. 1539-1546
Capacitance-voltage (C-V) and current-voltage (I-V) measurements were
used to study the effects of photocathodic charging of hydrogen in bor
on doped (4.5 x 10(16) cm-3) crystalline silicon. The electrolyte was
a 5% hydrofluoric solution. Within the first minutes of hydrogenation,
a negative charge variation occurs at the surface, due to the formati
on of a thin hydride-like layer. The hydrogen charging over an extende
d period of time (congruent-to 30 h) results in a drastic increase in
the reverse dark current I(D). This effect can be totally suppressed w
hen the electrodes are stepped to rest-potential (0 bias) for about 20
min. The resulting I-V characteristics are similar to those obtained
f or a nonhydrogenated sample. However, the surfaces exhibit a rough a
spect, and ellipsometry measurements show that an amorphized layer is
present. Secondary ion mass spectrometry measurements reveal that hydr
ogen (deuterium) is also injected up to 100 nm depth. It is concluded
that an amorphous hydrogenated layer forms during an electrolytical ch
arging, due to the incorporation of a high density of hydrogen atoms w
ithin the surface region. The raise of I(D) is ascribed to hydrogen-in
duced defects, operating as electron-hole generation centers. This lay
er partly dissolves when the cathodic polarization is removed (0 bias
condition) and consequently I(D) vanishes.