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

We report on the transport properties of a high mobility two- dimensional hole system (2DHS) confined in GaAs/AlGaAs quantum wells grown molecular-beam epitaxy on the [100] surface of GaAs. The quantum wells are modulation-doped with carbon utilizing a novel resistive filament source. At T=0.3K and carrier density p=1x1011cm-2, a mobility of 106cm2/Vs is achieved. At fixed carrier density p=1011cm-2, the mobility is found to be a non- monotonic function of the quantum well width. The mobility peaks at 106cm2/Vs for a 15nm well and is reduced for both smaller and larger well widths for these [100] samples. The mobility anisotropy is found to be small. Mobility along [011] is approximately 20% higher than along the [011] direction. In addition, the low temperature carrier density is found to have low sensitivity to light. The hole density increases by only ~10% after exposure to red light at T=4.2K. In structures designed for a lower carrier density of 3.6x1010cm-2, a mobility of 800,000cm2/Vs is achieved at T=15mK.