Electronic transport in Si and Ge polymers

Time-resolved transport studies which have now been carried out on a wide variety of alkyl- and aryl-substituted Si and Ge backbone polymers demonstrate the ability of these unipolar systems to transmit holes through the specimen bulk with negligible loss of these positive carriers to deep traps, making these materials attractive candidates for electronic device applications. Transport has been studied by measuring drift mobilities as a function of field, temperature and composition, using the small-signal time-of-flight technique. Transport occurs among chain backbone derived states, yet exhibits behavior essentially identical to systems in which transiting carriers are known to undergo thermally activated tunneling transitions among discrete molecular sites. On this basis it is suggested that disorder causes the chain backbone to be sub-organized into domain-like units of varying conjugation length. The sensitivity of transport to large-scale thermodynamic processes, side-group substituent and effect of specific dopants is demonstrated.