In organic solids, hopping transport is known to be a primary conduction mechanism. The prominent feature of hopping transport is its low mobility, which has been major limitation of utilizing organic solid as an active channel material. However, it has been known@footnote 1@ that, with efficient @pi@-@pi@ stacking of @pi@-conjugated molecules, the mobility of organic solids can be dramatically improved. To realize this idea, highly pure single crystals of organic molecules have been used to demonstrate much higher mobility,@footnote 2@ but it is questionable whether it would be feasible to fabricate a 3-terminal device with reasonable operating voltage. Another suggested solution is to use well-ordered self-assembled monolayer (SAM) of @pi@-conjugated molecules as an active channel component. In this study, a testbed for hopping transport through SAM has been fabricated using back-to-back schottky diode structure on semi-insulating GaAs. Before depositing molecules, pre-deposition current is less than 1nA. After forming SAM on GaAs surface, significant change in conductivity was observed in several molecules. For instance, thiophenol SAM increased conductivity by ~10 times, whereas ODT SAM suppressed bulk leakage current by one third. There are two possible conduction paths that can explain this conductivity increase: 1) hopping conduction through SAM 2) surface potential change due to the molecular dipole moments. However, it is not likely that the second possibility is a primary reason for enhanced conductivity because of the fact that ODT SAM, which has relatively strong molecular dipole moment but no @pi@-electrons, decreased conductivity. In addition, the dependence of mobility on temperature indicates that hopping transport is dominant. Finally, the application of the testbed to chemical sensors and organic transistors will be discussed. @FootnoteText@ @footnote 1@ J. L. Bredas, et al., PNAS, 99, 5084 (2002)@footnote 2@ Vikram C. Sundar, et al., Science, 303, 1644 (2004).