Heating of Two-Dimensional Holes in SiGe and the B = 0 Metal-Insulator Transition

We study the resistivity vs. electric field dependence �(E) of a 2D hole system in SiGe close to the B = 0 metal-insulator transition. Usingas a "thermometer" to obtain the effective temperature of the holes Te(E), we find that the �(E) dependence can be attributed to hole heating. The hole-phonon coupling involves weakly screened piezoelectric and deformation potentials compatible with previous measurements. The damping of the Shubnikov-de Haas oscillations gives the same Te values. Thus the �(E) dependence and the E-field "scaling" do not provide additional evidence for a quantum phase transition (QPT). We discuss how to study, in general, true E-field scaling and extract the ratio of the QPT characteristic lengths.