Fractional quantum Hall effect in organic molecular semiconductors

High-quality crystals of the organic molecular semiconductors tetracene and pentacene were used to prepare metal-insulator-semiconductor (MIS) structu res exhibiting hole and electron mobilities exceeding 10(4) square centimet ers per volt per second, The carrier concentration in the channel region of these ambipolar field-effect devices was controlled by the applied gate vo ltage. Well-defined Shubnikov-de Haas oscillations and quantized Hall plate aus were observed for two-dimensional carrier densities in the range of 10( 11) per square centimeter. Fractional quantum Hall states were observed in tetracene crystals at temperatures as high as similar to 2 kelvin.