TIME-RESOLVED STUDIES OF ELECTRONIC TRANSPORT IN SI AND GE BACKBONE POLYMERS

Time-resolved transport studies in alkyl- and aryl-substituted Si and Ge polymers, together with xerographic discharge measurements, clearly demonstrate the ability of a wide variety of these polymers to transmit holes, photogenerated (or photoinjected) at one surface under an applied field, through the film bulk to the opposite surface with negligible loss of these carriers to deep traps. The average carrier velocity per unit field (i.e., the drift mobility mu) is measured by the small-signal current-mode time-of-flight technique (TOF). Two key results are discussed in detail: (1) the mechanism of electronic transport in the glassy state, which is established to be hopping among energetically inequivalent sites on the polymer main chain (rather than band motion); and (2) elucidation of the mechanism by which drift mobility in a given polymer can be modified by chemical doping.