Metal-insulator transition in Si inversion layers in the extreme quantum limit

We report magnetotransport data of an insulating phase in silicon inversion layers in the extreme quantum limit at a Landau-level filling factor of ν≲1/2. The transport properties have proved to be unexpectedly similar to those of the insulating phase in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterostructures around ν=1/5 (for electron gas) and ν=1/3 (for hole gas) where magnetically induced Wigner solid formation has been reported. Strongly nonlinear current-voltage characteristics display threshold behavior and tend to saturate as current increases. The similarity of transport properties might strongly suggest the formation of a pinned electron solid in Si inversion layers at ν≲1/2. However, in the presence of a long-range potential, at ν=1/2 the percolation metal-insulator transition is expected. Both the magnetically induced electron solid formation and the percolation transition are considered as possible explanations of the observed effects.