Impact of short-range scattering on the metallic transport of strongly correlated two-dimensional holes in GaAs quantum wells

Understanding the nonmonotonic behavior in the temperature dependent resistance $R$$\left(T\right)$ of strongly correlated two-dimensional (2D) carriers in clean semiconductors has been a central issue in the studies of 2D metallic states and metal-insulator transitions. We have studied the transport of high mobility 2D holes in 20-nm-wide GaAs quantum wells with varying short-range disorder strength by changing the Al fraction $x$ in the ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}$As barrier. Via varying the short-range interface roughness and alloy scattering, it is observed that increasing $x$ suppresses both the strength and characteristic temperature scale of the 2D metallicity, pointing to the distinct role of short-range vs long-range disorder in the 2D metallic transport in this correlated 2D hole system with interaction parameter $r_s\sim 20$.

Figure 1

Longitudinal resistance $R_{xx}$ vs $T$ of 2D holes in a 20-nm-wide GaAs quantum well with Al mole fractions of (a) 7% and (b) 13% in the ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}$As barrier. The dotted lines mark $T_0$, the position of the peak in $R_{\mathrm{xx}}\left(T\right)$.

Figure 2

(a) The temperature dependent resistance, normalized with $R_0$, for 20-nm-wide GaAs quantum wells with 7%, 10%, and 13% Al mole fractions at $p$ = 1.77, 1.73, and 1.71 × 10${}^{10}$ cm${}^{-2}$, respectively. The model fit of Eq. (1) is indicated by the solid lines. The inset plots the unnormalized resistance as a function of temperature. (b) Dependence of the strength of 2D metallicity as defined by the ratio of resistance at the peak of $R\left(T\right)$ and residual resistance on the hole density. The error bar comes from averaging measurements from different current/voltage configuration and different samples. Zero-bias densities are the maximum densities for each Al%.

Figure 3

Characteristic temperature $T_0$ vs 2D hole density for various GaAs QWs with different Al fraction in barrier, where $T_0$ represents the temperature at which $R_{xx}\left(T\right)$ peaks.

Figure 4

The dimensionless, $T$-dependent part of the electronic contribution to $R_{xx}$, normalized to the height of the resistance peak in $R_{xx}\left(T\right)$, plotted against temperature normalized with the characteristic temperature $T_0$.