Monte Carlo simulations of low-field hole transport in strained InGaAs quantum wells

Abstract

The authors report on Monte Carlo simulations of low-field hole transport at 77 K in InGaAs-AlGaAs quantum wells of different widths and alloy compositions. The valence subband structure is obtained using a k.p method within the infinite well approximation, which accounts for mixing between heavy and light hole states. The effect of alloy, impurity and phonon scattering are included in the transport simulations. Although the infinite well approximation is only expected to be reliable for barriers with an aluminium fraction greater than about 0.4, for which the heavy hole well is sufficiently deep, the results show good agreement with experimental measurements for a finite 90 AA In0.18Ga0.82As-GaAs quantum well. A study of hole transport in 90 AA InxGa1-xAs wells (0.10<or=x<or=0.25) predicts a mobility which increases with indium concentration since the reduction in the effective mass of the highest HH1 subband due to strain more than compensates for the greater alloy scattering rate. An analysis of wells with 18% indium content and widths in the range 50-150 AA indicates a general increase in hole mobility with well width but with a local minimum around 90 AA due to intersubband scattering from the HH1 subband to the heavier HH2 subband.