Crystal growth and anisotropic resistivity of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_{2\mathrm{-}\mathit{x}}$${\mathrm{La}}_{\mathit{x}}$${\mathrm{CuO}}_{\mathit{y}}$

A number of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{La}}_{\mathit{x}}$ ${\mathrm{CuO}}_{\mathit{y}}$ crystals with different doping levels in the phase diagram have been grown and characterized by x-ray-diffraction measurements. The anisotropic resistivity was measured using a generalization of the Montgomery method and was found to change in a systematic way. Our analysis indicates that for all the samples the in-plane transport is on the metallic side of the Ioffe-Regel criterion, but the out-of-plane transport is deeply on the insulating side of the Mott limit. The temperature dependence of c-axis resistivity ${\mathrm{\rho }}_{\mathit{c}}$(T) can be well understood from the incoherent hopping model proposed by Levin and co-workers. The evolution of ${\mathrm{\rho }}_{\mathit{c}}$(T) with reduction in doping level is related to the reducing of both the impurity- and boson-assisted hopping processes. © 1996 The American Physical Society.