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

Abstract

Here, we analyse the effect of structure parameters like well width (w), central barrier width (b), and alloy concentration (x) on multisubband electron mobility μ 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 × 1018 cm−3) and N d2 (2 × 1018 cm−3). The mobility μ is calculated by considering ionised impurity (imp) and alloy disorder (ad) scattering mechanisms. The continuous variation of x inside the well makes μ ad < μ imp resulting in the dominance of ad-scattering on μ as a function of N d1. As a result, at the interface an increase in x from 0.1 to 0.3 reduces μ around 40%. However, an increase in w symmetrically (w 1 = w 2) enhances μ. Further, the introduction of non-symmetric well profile (w 1 ≠ w 2) not only causes asymmetric redistribution of subband wave functions ψ 0 and ψ 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 Å to 80 Å has a marginal effect on μ during single subband occupancy but improves μ during double subband occupancy through intersubband interaction.