Effect of parabolic structure potentials on electron mobility in AlxGa1-xAs quantum well based field effect transistor structure

Abstract

Here, we theoretically calculate and analyze electron mobility μ in AlxGa1-xAs double parabolic and semi-parabolic quantum well (DPQW and DSPQW) based field effect transistor structures. We compute μ as a function of applied electric field F by considering ionized impurity (II) and alloy disorder (AL) screened scattering potentials (VscrII/AL) and show that μ(DPQW) > μ (DSPQW). The symmetric property of VscrII/AL makes μ to vary symmetrically around F = 0 at which two subbands are occupied. The shape of the DSPQW structure potential, compared to DPQW, causes the subband wave functions ψ0 and ψ1 to lie nearer and also penetrate more into the central barrier. Accordingly, the II-scattering is reduced due to increased distance of the electrons from the ionized donors (lying in the side barriers), while AL-scattering is enhanced through increased scattering in the central barrier. As a result, we obtain for F = 0, μII (DSPQW) > μII (DPQW) and μAL (DSPQW) < μAL (DPQW). Further, we show that μ enhances in DPQW by increasing design parameters such as well width, spacer width, and central barrier width. However, μ reduces with the increase in alloy concentrations inside the well through intersubband interaction. The obtained results reflect the suitability of parabolic potential based quantum well structures in emerging optoelectronic devices to enhance the transport and optical properties.