RECOMBINATION DYNAMICS AT INP LIQUID INTERFACES

The relaxation dynamics of photoexcited charge carriers at the interfa ce between InP and several metal ion solutions has been studied using picosecond time-resolved photoluminescence and electrochemical techniq ues. The results show that for p-InP, the controlling recombination pr ocess follows the nonradiative Shockley-Read-Hall (SRH) mechanism, whi le on the other hand, radiative bulk recombination is the controlling process in n-type crystals. The surface recombination velocities (SRV) of both conductivity types were found to be strongly dependent (varyi ng over the range of 500 to 2 x 10(5) cm/s) on the ionic solution comp osition and concentration. The SRV of the etched n-InP surface is reta ined and remains low when it is in contact with nonoxidizing ions like Zn2+ or Cr3+. On the other hand, for n-InP, the SRV increases sharply when the crystal is dipped into stronger oxidizing species like Ag+ ( SRV = 1.4 x 10(5) cm/s) or Cu2+ (SRV = 3.4 x 10(4) cm/s). The electroc hemical measurements provided firm evidence for chemisorbed-induced su rface states in the case of the more strongly oxidizing solutions. The distribution of the surface states was extracted from a frequency dis persion analysis of the electrodes' impedance and was found to correla te with the SRVs. We discuss the SRV dependence on the redox potential s of the various solutions and the similarity of the results to those obtained in the past for CdS and CdSe.