Exploration of the Limits to Mobility in Two-Dimensional Hole Systems in GaAs/AlGaAs Quantum Wells

摘要

We report on the growth and electrical characterization of a series oftwo-dimensional hole systems (2DHSs) used to study the density dependence oflow temperature mobility in 20 nm GaAs/AlGaAs quantum wells. The hole densitywas controlled by changing the Al mole fraction and the setback of thedelta-doping layer. We varied the density over a range from 1.8 $\times$10$^{10}$ cm$^{-2}$ to 1.9 $\times$ 10$^{11}$ cm$^{-2}$ finding a nonmonotonicdependence of mobility on density at T = 0.3 K. Surprisingly, a peak mobilityof 2.3 $\times$ 10$^6$ cm$^2$/Vs was measured at a density of 6.5 $\times$10$^{10}$ cm$^{-2}$ with further increase in density resulting in reducedmobility. We discuss possible mechanisms leading to the observed non-monotonicdensity dependence of the mobility. Relying solely on interface roughnessscattering to explain the observed drop in mobility at high density requiresroughness parameters which are not consistent with measurements of similarelectron structures. This leaves open the possibility of contributions fromother scattering mechanisms at high density.