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

TL;DR

This paper reports on the high mobility of two-dimensional hole systems in GaAs/AlGaAs quantum wells grown on (100) GaAs substrates, highlighting the effects of well width, anisotropy, and light exposure on transport properties.

Contribution

It introduces a novel resistive filament source for modulation doping with carbon and characterizes the mobility dependence on well width and orientation in (100) GaAs substrates.

Findings

Achieved mobility of 10^6 cm^2/Vs at 0.3K and p=1x10^11cm^-2

Mobility peaks at 15nm well width and is slightly anisotropic

Low sensitivity of hole density to light exposure

Abstract

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=1x10^11cm^-2, a mobility of 10^6cm^2/Vs is achieved. At fixed carrier density p=10^11cm^-2, the mobility is found to be a non-monotonic function of the quantum well width. The mobility peaks at 10^6cm^2/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 (0\bar11) 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 3.6x10^10cm^-2, a mobility of 800,000cm^2/Vs is achieved at T=15mK.