Effect of structure parameters on electron mobility in asymmetric V-shaped double quantum well structure

Here, we analyse the effect of structure parameters like well width (w), central barrier width (b), and alloy concentration (x) on multisubband electron mobility mu in a GaAs-AlxGa1-xAs based modulation doped asymmetric V-shaped-double-quantum-well (VDQW) structure. The asymmetry in the structure potential is generated through the difference in the doping concentrations (N ( d )) in the side barriers i.e., N ( d1) (0 to 4 x 10(18) cm(-3)) and N ( d2) (2 x 10(18) cm(-3)). The mobility mu is calculated by considering ionised impurity (imp) and alloy disorder (ad) scattering mechanisms. The continuous variation of x inside the well makes mu ( ad ) < mu ( imp ) resulting in the dominance of ad-scattering on mu as a function of N ( d1). As a result, at the interface an increase in x from 0.1 to 0.3 reduces mu around 40%. However, an increase in w symmetrically (w (1) = w (2)) enhances mu. Further, the introduction of non-symmetric well profile (w (1) not equal w (2)) not only causes asymmetric redistribution of subband wave functions psi (0) and psi (1) in the wells, but also changes the position and hence occupation of subband energy levels, thereby influencing the subband mobility. As the difference in w (1) and w (2) increases, the system becomes more and more single subband occupied as a function of N ( d1) and hence the mobility enhances due to the absence of intersubband scattering. Our results also reflected that an increase in b from 20 angstrom to 80 angstrom has a marginal effect on mu during single subband occupancy but improves mu during double subband occupancy through intersubband interaction.