PHOTOCURRENT MULTIPLICATION DURING PHOTODISSOLUTION OF NORMAL-SI IN NH4F - DECONVOLUTION OF ELECTRON INJECTION STEPS BY INTENSITY MODULATED PHOTOCURRENT SPECTROSCOPY

The photodissolution of n-Si in ammonium fluoride solutions occurs by a multistep electron transfer process in which photohole capture competes with electron injection from intermediate species, giving rise to quantum efficiencies (Q) greater than unity. The mechanism and kinetics of this photocurrent multiplication effect have been investigated in the steady state and by intensity modulated photocurrent spectroscopy (IMPS). Quantum efficiencies as high as 4 have been observed at low light intensities, and the rate constants for electron injection under these conditions have been derived by frequency response analysis of the IMPS data. The validity of the analysis is demonstrated by the fact that the steady state intensity dependence of the quantum yield predicted using the rate constants derived by IMPS agrees well with the experimental results. © 1990.