Ba. Balko et al., PICOSECOND PHOTOLUMINESCENCE STUDIES OF PHOTOCORROSION AND PASSIVATION OF N-GAAS IN NA2S-CONTAINING SOLUTIONS, Journal of physical chemistry, 99(12), 1995, pp. 4124-4131
Passivation of n-GaAs by Na2S in an electrochemical cell has been stud
ied using photoluminescence decays and voltage dependence of photolumi
nescence;lescence intensity. A significant increase in the degree of p
assivation of the (100) n-GaAs surface is seen when the concentration
of Na2S is increased above similar to 1 M. The observed passivation in
higher concentrations of Na2S eventually deteriorates with extended e
xposure to light. The corrosion that develops when the n-GaAs is in hi
gher concentrations of Na2S leads to traps that can be occupied at all
voltages. This behavior is different from corrosion seen in lower con
centrations of Na2S in which the traps can only be occupied at voltage
s greater than V = 0.0 V. Decay measurements at flatband potential and
at open circuit indicate no significant changes in surface-trapping v
elocity as the Na2S concentration is changed from 0.008 to 1 M. This s
uggests that repinning or removal of surface traps is not responsible
for the passivation that is observed upon increasing the Na2S concentr
ation. An increase in the rate of charge transfer across the interface
as the Na2S concentration in the electrolyte is increased appears res
ponsible.