In this paper, we report the theoretical predictions of a high-index GaAs
substrate ((111)A and (311)A) on the subband structure and thereafter on the
2D electron density of Si δ-doped
Al0.33Ga0.67As/In0.15Ga0.85As/GaAs pseudomorphic high
electron mobility transistor (pHEMT) with an additional
InxGa1-xAs
(x > 0.15) thin layer embedded in the channel. We have seen that the
electronic structures and the electron density are quite sensitive to the
additional InxGa1-xAs
(x > 0.15) layer thickness, indium
composition and to their position in the channel. An optimal position of the
additional InxGa1-xAs
layer was found to be corresponding to the
maximum of the first eigen envelope function for the different growth
directions. We report that the optimised electron density is obtained in the
structure grown on (111)A GaAs substrate. In this case the electron transfer
is significantly higher than those grown on (311)A and (001) GaAs substrates
respectively.