Electron mobility inGa1−xAlxAsalloys

Hall mobilities in high-purity epitaxial layers of $n$-type ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ with room-temperature electron concentration in the range (5-10)×${10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$ have been measured for alloy compositions $x$ in the range $0\le x\le 0.78$ and in the temperature interval $15\lesssim T\lesssim 300$ K. Models for the variation of various material parameters with $x$ are developed and it is shown that the alloy scattering potential is ∼0.3 eV and is weakly dependent on $x$. The data have been analyzed and it has been shown that alloy, space charge, and intervalley scatterings play an important role in limiting the electron mobility. The data suggest that the deep energy levels in ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ behave as space-charge scattering centers.