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 hole system (2DHS) confined in GaAs/AlGaAs 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 X 10~(11) cm~(-2), a mobility of 10~6 cm~2/Vs is achieved. At fixed carrier density p=10~(11) cm~(-2), the mobility is found to be a nonmonotonic function of the quantum well width. The mobility peaks at 10~6 cm~2/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 [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=4.2 K. In structures designed for a lower carrier density of 3.6 X 10~(10) cm~(-2), a mobility of 800 000 cm~2/Vs is achieved at T=15 mK.