Magnetotransport in low-densityp−Si∕SiGeheterostructures: From metal through hopping insulator to Wigner glass

Abstract

We study DC and AC transport in low-density p−Si/SiGe heterostructures at low temperatures and in a broad domain of magnetic fields up to 18 T. Complex AC conductance is determined from simultaneous measurement of velocity and attenuation of a surface acoustic wave propagating in close vicinity of the 2D hole layer. The observed behaviors of DC and AC conductance are interpreted as an evolution from metallic conductance at B = 0 through hopping between localized states in intermediate magnetic fields (close to the plateau of the integer quantum Hall effect corresponding to the Landau-level filling factor ν=1) to formation of the Wigner glass in the extreme quantum limit (B 14, T 0.8 K).

Magnetoresistivity and acoustoelectronic effects in a tilted magnetic field in p-Si/SiGe/Si structures with an anisotropic g factor

“…The formation of pinned Wigner glass was revealed in p-Si/SiGe/Si with a low impurity concentration (p= 8.2 × 10 10 cm −2 ) in the quantum limit in a perpendicular magnetic field [8], and a giant positive magnetoresistivity was observed in this structure in a parallel magnetic field [9]. This magnetoresistivity was caused by the interaction of the orbital motion of carriers in a wide quantum well with a parallel magnetic field.…”

Large magnetoresistance of a dilutep-Si/SiGe/Siquantum well in a parallel magnetic field

“…It consisted of the 300 nm Si buffer layer followed by 30 nm Si 0.92 Ge 0.08 layer (sample with p=8.2×10 10 cm −2 ) or Si 0.87 Ge 0.13 layer (sample with p=2×10 11 cm −2 ), 20 nm undoped spacer and 50 nm layer of B-doped Si with doping concentration 2.5×10 18 cm −3 . Magnetoresistance of the sample with p=8.2×10 10 cm −2 was studied in detail earlier in wide range of transverse magnetic fields and temperatures 15 . At the field B=0 T the resistance in both samples demonstrated a metallic behavior.…”

Magnetoconductivity in a Disordered and Interacting 2D p-SiGe Quantum Well

“…As shown in Fig. 1 ,this heterostructure is constituted by the stacking of the following four layers: a Si buffer layer, Si 0.92 Ge 0.08 layer, undoped spacer and layer of B-doped Si with a doping concentration of 2.5 × 10 18 cm −3 , whose consecutive thickness are: 300 nm, 30 nm, 20 nm and 50 nm, respectively [11,12]. This structure makes possible the production a two-dimensional gas of holes in the SiGe with a carrier density of p = 8.2 × 10 14 m −2 and a hole mobilty of μ = 1 × 10 4 cm 2 V −1 s at liquid-helium temperatures.…”

“…This structure makes possible the production a two-dimensional gas of holes in the SiGe with a carrier density of p = 8.2 × 10 14 m −2 and a hole mobilty of μ = 1 × 10 4 cm 2 V −1 s at liquid-helium temperatures. The dc magnetoresistance measurements were carried out under a magnetic field parallel to the 2D hole-gas plane [11,12].…”