Growth and Fabrication of ultra-high mobility in-situ back-gated two-dimensional electron gases
Investigations of the energy scales of many-body phenomena in high mobility two-dimensional electron gases (2DEGs) often require the ability to tune the electron density in a single device. Electrostatic gating is often the method of choice, but traditional device designs are less than ideal. The 2DEG density in top-gated devices is often hysteretic and/or unstable over time due to intervening doping layers, and traditional back-gates applied to mechanically thinned substrates typically require large gate voltages (∼ 100 V) to achieve significant modulation of the electron density due to the large gate-channel separation (∼ 150 μm). This project focuses on the growth of high mobility 2DEGs in 30 nm GaAs/AlGaAs quantum wells in which the density is modulated by an in-situ grown back-gate. Such in-situ gates can be grown close to the 2DEG (∼ 1 μm) and without doping layers between the 2DEG and gate. These structures exhibit high mobilities (> 10^7 cm^2/Vs) and high quality magneto-transport which makes them an ideal system for studying electron interaction effects as a function density.