Molecular-beam-epitaxial growth of n-AlGaAs on clean Cl2-gas etched GaAs surfaces and the formation of high mobility two-dimensional electron gas at the etch-regrown interfaces

By using an ultrahigh vacuum multichamber process system, very clean GaAs surface is successfully prepared by chlorine-gas etching and AlGaAs is subsequently grown by molecular beam epitaxy to show that two-dimensional electron gas is successfully formed at etch-regrown AlGaAs/GaAs interface. Mobility as high as 114 000 cm2/V s at 9.8 K is achieved for the carrier concentration NS=4.5×1011 cm−2. From the secondary-ion-mass-spectroscopy measurement, the carbon concentration at the interface is estimated to be 2×1010 cm−2, and is found to be a dominant scatterer for the two-dimensional electrons. A transmission-electron-microscope image has evidenced a very flat feature of etch-regrown interface.