Electron mobility in asymmetric GaN/AlGaN quantum well transistor structure: effect of alloy disorder scattering

Abstract

We analyze the electron mobility μ of GaN/AlGaN based quantum well (QW) transistor structure. We consider the potential profile V(z) by including the potential due topolarization (V p ) and Hartree potential (V H ) owing to surface electron density N s . The low temperature mobility is governed by the alloy disorder (ad-) and interface roughness (ir-) scatterings. As N s increases, μ increases. However, for larger N s (N s > 0.6 × 1013 cm−2), there is a deviation showing decreasing trend of μ. We show that the ad- scattering plays a vital role in governing μ. An increase in N s causes narrowing of the polarization induced channel potential through V H and hence facilitates the larger extension of the subband wave function into the surface barrier. Accordingly, the ad-scattering increases, thereby reducing μ. we show that with an increase in well width there is a substantial rise in μ in quantum well (QW) structures while almost no change in μ in double heterostructures (DH). Enhancement of height of the barriers leads to different results, i.e., for the back barrier, there is a reduction in μ in both QW and DH structures, while for the surface barrier, there is a rise in μ. The fascinating trends of our results of μ in different GaN/AlGaN structures elucidate the importance of ad-scattering on low temperature μ.