Lowhyphen; and highhyphen;field transport properties of pseudomorphic InxGa1minus;xAs/In0.52Al0.48As (0.53le;xle;0.65) modulationhyphen;doped heterostructures

摘要

We have grown pseudomorphic InxGa1minus;xAs/In0.52Al0.48As modulationhyphen;doped heterostructures by molecularhyphen;beam epitaxy under carefully controlled growth conditions. Mobilities as high as 13thinsp;900, 74thinsp;000, and 134thinsp;000 cm2/Vthinsp;s are measured at 300, 77, and 4.2 K in a heterostructure withx=0.65. Shubnikovndash;de Haas measurements indicate that the change in the effective mass with increasing In is not significant and is not responsible for the enhancement in mobilities. We believe that the improvement results from reduced alloy scattering, reduced intersubband scattering, and reduced impurity scattering, all of which result from a higher conductionhyphen;band offset and increased carrier confinement in the twohyphen;dimensional electron gas. The highhyphen;field electron velocities have been measured in these samples using pulsed currenthyphen;voltage and pulsed Hall measurements. A monotonic increase in velocities is observed both at 300 and 77 K with an increase of In content in the channel. Velocities of 1.55times;107and 1.87times;107cm/s are measured at 300 and 77 K, respectively, in a In0.65Ga0.35As/In0.52Al0.48As modulationhyphen;doped heterostructure.