Kp. Quinlan, THE MECHANISM OF THE PHOTOELECTROCHEMICAL ETCHING OF P-INP IN NITRIC-ACID SOLUTIONS, Journal of the Electrochemical Society, 144(10), 1997, pp. 3469-3473
The mechanism of the photoelectrochemical (PEG) etching of p-InP in ni
tric acid was investigated. The success of the procedure is shown to b
e due to the chemical oxidation of the photoproduced metallic indium b
y nitric acid. The study gives insight into how the photoreduction of
p-InP and protons occur simultaneously Plots of the etch rate vs. nitr
ic acid concentration for two p-InP electrodes with different carrier
concentrations and etch pit densities (EPD) indicated that defects pla
y a role in the photoreduction process. The effect of EPD on the photo
reductions;has been interpreted in terms of surface states which origi
nate from EPD; the EPD are correlated with the magnitude of the surfac
e states. The total number of coulombs passed in the PEC etching regio
n was found to be relatively constant for each p-InP electrode. Compar
ison of the charge transferred with the PEC etch rates indicated that
the majority of protons are photoreduced via surface states. A positiv
e shift of the onset potential for photocurrent with increasing nitric
acid concentrations implied a decrease in the density of surface stat
es. This observation was correlated with the participation of the cond
uction band in the photoreduction of p-InP. At higher nitric acid conc
entrations, experiments indicate that the photoreduction of protons is
possible at both the surface states and conduction band. Energy diagr
ams lend support to these suppositions.