High mobility two-dimensional hole system in GaAs/AlGaAs quantum wells grown on (100) GaAs substrates

摘要

We report on the transport properties of a high mobility two-dimensional holesystem (2DHS) confined in GaAs/AlGaAs quantum wells grown molecular-beamepitaxy on the (100) surface of GaAs. The quantum wells are modulation-dopedwith carbon utilizing a novel resistive filament source. At T=0.3K and carrierdensity p=1x10^11cm^-2, a mobility of 10^6cm^2/Vs is achieved. At fixed carrierdensity p=10^11cm^-2, the mobility is found to be a non-monotonic function ofthe quantum well width. The mobility peaks at 10^6cm^2/Vs for a 15nm well andis reduced for both smaller and larger well widths for these (100) samples. Themobility anisotropy is found to be small. Mobility along (0\bar11) isapproximately 20% higher than along the (011) direction. In addition, the lowtemperature carrier density is found to have low sensitivity to light. The holedensity increases by only ~10% after exposure to red light at T=4.2K. Instructures designed for a lower carrier density of 3.6x10^10cm^-2, a mobilityof 800,000cm^2/Vs is achieved at T=15mK.