Thermopower of ap-typeSi/Si1−xGe

Diffusion Thermopower of a Two-Dimensional Hole Gas in SiGe in a Quantum Hall Insulating State

“…By applying a substrate bias, measurements could be made at two different densities: p 1:9 10 15 m ÿ2 and p 2:4 10 15 m ÿ2 . The mobilities were strongly temperature dependent [12] and at 1 K they were 1.3 and 1:5 m 2 =V s, respectively. Conductivity and TEP measurements at zero field show that at the sample densities used here there is no sign of localization (seen for p < 1:0 10 15 m ÿ2 [11]) and metallic conductivity prevails down to the lowest temperature.…”

“…The factor used to convert the ac data to absolute thermopower was determined by comparing ac and dc measurements at zero field. An analysis of both the temperature dependence of TEP at zero field and the temperature and field dependence of the quantum oscillations in the TEP at low fields [12] shows that phonon drag becomes negligible below 0.7 K, leaving diffusion as the dominant driving mechanism at low temperatures. In this Letter, we focus on the behavior at higher fields, especially in the field-induced insulating phase around 1:5.…”

Diffusion thermopower of a p‐type Si/Si1–xGex heterostructure at zero magnetic field

“…In our HS, the 2D hole gas is confined by a triangular potential [1,11] located along the growth direction chosen as the z -axis with the Si/SiGe interface locates at 0 z = . It has been shown [12] that for the finite barrier potential 0 V , the lowest subband may be very well described by the modified Fang-Howard wave function [9,10,12]: (9) in which k and κ are half of the wave numbers in the well and barrier, respectively.…”

“…In a recent experiment, the thermopower of the two-dimensional (2D) hole gas in a p-type Si/Si 0.88 Ge 0.12 heterostructure (HS) were reported [1]. At very low temperature, the total thermopower S , approximated by the diffusion thermopower d S , was explained by a phenomenological model without calculations starting from the microscopic level [1].…”

“…At very low temperature, the total thermopower S , approximated by the diffusion thermopower d S , was explained by a phenomenological model without calculations starting from the microscopic level [1]. Since many theoretical studies [2,3] of the diffusion thermopower are available, it may be interesting if one can use them to examine the reported data.…”