The effect of structural parameters and growth temperature on the electron density in asymmetric double-2DEGs

We report on growth and low-temperature transport of Ga(Al)As-based asymmetric double two-dimensional electron gas (2DEG) structures consisting of a quantum well (QW) stacked on top of a normal heterojunction. Our data show that the electron density of both parallel 2DEGs can be reliably matched just by varying a single growth parameter namely the width of spacer 2 which determines the electron density in the QW. This finding is independent of growth temperature and QW width although segregation of Si dopant atoms especially at elevated growth temperatures has a remarkable impact on the QW electron density. The best sample with exact match of the carrier densities exhibits metrological quality of the quantized Hall resistance with a relative standard deviation of five parts in 109 from the nominal value RK-90/4 at filling factor 2.