Modulation doped n-AlGaAs/GaAs heterostructures grown by flow-rate modulation epitaxy

Flow-rate Modulation Epitaxy was applied to grow GaAs, AlAs, AlGaAs layers and n-AlGaAs/GaAs modulation doped heterostructures. This method considerably reduced the growth temperature, and high-quality GaAs and AlAs layers were obtained at the growth temperature as low as 550°C. Al_xGa_1-x As alloy layers, where x=n/(n + m), were formed by repeating the growth of m-monolayers of GaAs followed by the growth of n-monolayers of AlAs. Thus, the Al_xGa_1-xAs layers are no longer “random alloys” but have “ordered structures”. It was found that, in Flow-rate Modulation Epitaxy, the Si doping efficiency to Alo.25Gao.75As is quite high, and is almost constant in the growth temperature range between 500 and 625 °C. Using this method, we fabricated modulation doped n-AlGaAs/GaAs heterostructures. At the growth temperature of 550°C, the 2DEG mobility as high as 7 X 10⁴cm²/Vs was obtained at 6 K.