IMPEDANCE ANALYSIS OF SURFACE-MODIFIED GA0.5IN0.5P - AQUEOUS-ELECTROLYTE INTERFACE

In this work electrochemical impedance spectroscopy was carried out on pre- and post-etched Ga0.5In0.5P (1.8-1.9 eV) as well as quinolinol-m odified surfaces, over seven decades of frequencies. The spectra were examined in the Bode as well as complex impedance planes and deconvolu ted using nonlinear-least-squares fitting to obtain equivalent circuit s that isolated the space charge from the surface states. Chemical wet -etching of Ga0.5In0.5P was found to remove surface states as evidence d in the removal of the low frequency time constant from the spectra. Treatment with 8-quinolinol was found to shift the flat-band potential in the positive direction vs. she by about 300 mV in near neutral ele ctrolytes.