Density of two-dimensional electron gas in modulation-doped structure with graded interface

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Abstract
We have calculated the concentration nso of the two-dimensional gas in the AlGaAs/GaAs modulation-doped structures with graded heterointerfaces. Our calculation shows that nso increases with the increase in the grading length WGR at small values of WGR. Depending on composition and doping of the AlGaAs layer the maximum value of nso is achieved for WGR between 20 and 70 Å. An increase in the concentration of the 2-d gas leads to a larger device transconductance and to a large current swing. Hence, the device performance may be improved by grading the heterointerface.