Modulation Doped n-AlGaAs/GaAs Heterostructures Grown by Flow-rate Modulation Epitaxy

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Abstract
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 x Ga1-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 x Ga1-x As layers are no longer “random alloys” but have “ordered structures”. It was found that, in Flow-rate Modulation Epitaxy, the Si doping efficiency to Al0.25Ga0.75As 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 7×104 cm2/Vs was obtained at 6 K.