Heterostructure Design for High Two-dimensional Electron Density in GaAs/AlGaAs Quantum Wells at Large Hydrostatic Pressures*

The application of hydrostatic pressure to GaAs/AlGaAs heterostructures has been a topic of great interest due to the possibility of achieving a g-factor ≈ 0 in high-quality, two-dimensional electron systems (2DESs). Despite the exciting prospect of studying electron-electron interactions in the absence of spin splitting, there are very few experimental reports on this subject. This is because in standard modulation-doped GaAs/AlGaAs heterostructures, the 2DES density decreases significantly as the magnitude of hydrostatic pressure applied to the system is increased. Here, we present a heterostructure design that circumvents such density degradation, so that high-density, high-quality 2DESs can be obtained at large hydrostatic pressures. We show that by implementing this scheme, the 2DES density only decreases by ~ 4 x 10¹⁰ cm^-2 even at a hydrostatic pressure of 8.2 kbar. This is a factor of ~4 improvement compared to conventional structures. We will also present low-temperature magnetotransport data that demonstrate the high quality of our samples at large hydrostatic pressures.