Degenerate versus semi-degenerate transport in a correlated 2D hole system

TL;DR

This paper investigates the temperature-dependent transport properties of high mobility 2D hole systems in GaAs quantum wells, revealing a linear conductivity dependence on density and distinguishing between degenerate and semi-degenerate regimes.

Contribution

It introduces a model describing the conductivity in 2D hole systems across degenerate and semi-degenerate regimes, highlighting the roles of effective mobility and immobile carriers.

Findings

Conductivity is linearly dependent on density in both regimes.

Metallic conduction is linked to increased effective mobility at low T.

Resistivity decrease in semi-degenerate regime is due to reduced immobile carriers.

Abstract

It has been puzzling that the resistivity of high mobility two-dimensional(2D) carrier systems in semiconductors with low carrier density often exhibits a large increase followed by a decrease when the temperature ($T$) is raised above a characteristic temperature comparable with the Fermi temperature ($T_F$). We find that the metallic 2D hole system (2DHS) in GaAs quantum well (QW) has a linear density ($p$) dependent conductivity, $\sigma\approx e\mu^*(p-p_0)$, in both the degenerate (T<<T_F) and semi-degenerate (T T_F) regimes. The $T$-dependence of $\sigma(p)$ suggests that the metallic conduction (d$\sigma$/d$T<$0) at low $T$ is associated with the increase in $\mu^*$, the effective mobility of itinerant carriers. However, the resistivity decrease in the semi-degenerate regime ($T>T_F$) is originated from the reduced $p_0$, the density of immobile carriers in a two-phase picture.