Electrical properties of SrTiO₃/(Sr_1-x,La_x)TiO₃ superlattices grown by laser molecular beam epitaxy

We have successfully fabricated SrTiO₃/(Sr_1-x,La_x)TiO₃ (STO/SLTO) superlattices on step-terrace structured SrTiO₃, in which La defect is distributed in a regular manner of one dimension. The superlattices contain one unit cell thick SLTO layer with various stacking sequences. The charge carrier density of the superlattices was in the range of 1.7 × 10¹⁹-2 × 10¹⁶ cm^{- 3}. In addition, the mobility and resistivity of STO/SLTO superlattice were 11 cm²/Vs and 0.18 Ω cm at the STO₁/SLTO₁ stacking sequence, respectively. The charge carrier density of STO/SLTO superlattices increased significantly with the change in a stacking sequence, while the mobility is relatively insensitive to the change in the stacking sequence. The resulting resistivity of the superlattics changed significantly with the change in the stacking sequence due to mainly the change of the charge carrier density. The oxide superlattice approach provides an useful way of nonlinear control of charge carrier density and electrical resistivity.