FREE-CARRIER GENERATION IN SEMICONDUCTORS INDUCED BY ABSORPTION OF SUBBAND-GAP LIGHT

The mechanisms of electron-hole pair generation in a semiconductor ind uced by absorption of a subband-gap photon and mediated by a band-gap state are reviewed. The steady-state photocurrent quantum yield and th e photocurrent response to harmonic modulation of the light intensity are calculated for each mechanism. It is shown, with a nanoporous GaP photoanode as an example, that the mechanisms can be distinguished by intensity-modulated photocurrent spectroscopy and that characterizatio n of the mediating band-gap states is possible.