Drift velocity of electrons in quantum wells of selectively doped In$_{0.5}$Ga$_{0.5}$As/Al$_x$In$_{1-x}$As and In$_{0.2}$Ga$_{0.8}$As/Al$_x$Ga$_{1-x}$As heterostructures in high electric fields
Abstract:
The field dependence of drift velocity of electrons in quantum wells of selectively doped In$_{0.5}$Ga$_{0.5}$As/ Al$_x$In$_{1-x}$As and In$_{0.2}$Ga$_{0.8}$As/Al$_x$Ga$_{1-x}$As heterostructures is calculated by the Monte Carlo method. The influence of varying the molar fraction of Al in the composition of the Al$_x$Ga$_{1-x}$As and Al$_x$In$_{1-x}$As barriers of the quantum well on the mobility and drift velocity of electrons in high electric fields is studied. It is shown that the electron mobility rises as the fraction $x$ of Al in the barrier composition is decreased. The maximum mobility in the In0.5Ga0.5As/In0.8Al0.2As quantum wells exceeds the mobility in a bulk material by a factor of 3. An increase in fraction $x$ of Al in the barrier leads to an increase in the threshold field $E_{\mathrm{th}}$ of intervalley transfer (the Gunn effect). The threshold field is $E_{\mathrm{th}}$ = 16 kV/cm in the In$_{0.5}$Ga$_{0.5}$As/Al$_{0.5}$In$_{0.5}$As heterostructures and $E_{\mathrm{th}}$ = 10 kV/cm in the In$_{0.2}$Ga$_{0.8}$As/Al$_{0.3}$Ga$_{0.7}$As heterostructures. In the heterostructures with the lowest electron mobility, $E_{\mathrm{th}}$ = 2–3 kV/cm, which is lower than $E_{\mathrm{th}}$ = 4 kV/cm in bulk InGaAs.
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