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

We report on the transport properties of a high mobility two-dimensional hole system (2DHS) confined in GaAsAlGaAs quantum wells grown by molecular-beam epitaxy on the (100) surface of GaAs. The quantum wells are modulation doped with carbon utilizing a resistive filament source. At T=0.3 K and carrier density p=1× 1011 cm-2, a mobility of 106 cm2 Vs is achieved. At fixed carrier density p= 1011 cm-2, the mobility is found to be a nonmonotonic function of the quantum well width. The mobility peaks at 106 cm2 Vs for a 15-nm 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 [0 1- 1] 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=4.2 K. In structures designed for a lower carrier density of 3.6× 1010 cm-2, a mobility of 800 000 cm2 Vs is achieved at T=15 mK.