Optical Phonon Influence On The Mobility Of Electrons In AlN/GaN Quantum Wells

Based on the dielectric continuum phonon model, uniaxial model and Lei-Ting balance equation, the electronic mobility parallel to the interfaces for wurtzite (WZ) and zincblende (ZB) AlN/GaN quantum-well (QW) heterostructures is discussed by taking the influence of confined and interface phonon modes into account. The dependence of the electronic mobility on well width and temperature is presented.The electron-phonon interaction is dealt with the Frohlich matrix to obtain the mobility scattered by the confined optical phonon modes and the interface optical phonon modes in these QWs. It is shown from the computed results that the influence of the structure anisotropy on the mobility is obvious, and the total electronic mobility in a WZ QW is lower obviously than that in a ZB one. In consideration of structure influence on the electron effective mass, dielectric constants, band offsets between the well and barrier materials, and phonon frequencies to change the mobility, it is found that the variation of electron effective mass plays a very important role, while the other factors are less important.The numerical results also show that the two kinds of phonons mainly influence the mobility at different well width, respectively: the confined modes have the main role on the total mobility for wider QWs, as the well width deceases, the scattering from the interface phonons becomes stronger, at the same time the scattering from confined phonons becomes weaker. The contribution from interface phonon modes is dominant when the well width decreases below a critical value. In addition, it is also found that two symmetrical branches of interface phonons with high-frequency and low-frequency have contributions to the mobility for a ZB AlN/GaN QW, but only the former branch of phonons is important for a WZ one.