Measurements of Composite Fermion Conductivity Dependence on Carrier Density

We present the first experimental study of the carrier density dependence of the composite fermion conductivity $\sigma^{CF}_{xx}$ at Landau level filling factors $\nu= {1/2}$ and $\nu= {3/2}$ in high-quality front-gated GaAs/Al$_{0.33}$Ga$_{0.67}$As heterostructures. Extracting $\alpha$ from the power law ln$(\sigma^{CF}_{xx}) \propto$ ln$(n_e)^{\alpha}$ shows that $\alpha \approx 1$. The measured ${\alpha} \approx 1$ is placed between the predicted value 3/4 in the strong random magnetic field regime, and 3/2 in the weak random magnetic field regime. Comparisons between our results and theory are discussed.