Electron mobility modulated by optical phonons in Al_xGa_(1-x)N/In_yGa_(1-y)N/GaN/AlN heterostructures

摘要

The electron mobility influenced by optical phonons, the size of InGaN/GaN channels and In composition y in wurtzite Al_xGa_(1-x)N/In_yGa_(1-y)N/GaN/AlN heterostructures as basic structures of high electron mobility transistors (HEMTs) is investigated around room temperature. The electron states affected by the two-dimensional electron gas near the interfaces are obtained by self-consistently solving the Poisson and Schroedinger equations. Based on the dielectric continuum and Loudon's uniaxial crystal models combined with the transfer matrix methods, the dispersion relations and electrostatic potentials of interface (IF), confined (CO), half space, and propagating optical phonons are discussed in detail, as well as the corresponding transformations among different phonon modes. Furthermore, the mobility contributed by optical phonons is given by the Lei and Ting's force balance and energy balance equations. Our results show that the electron mobility in the heterostructures with composite InGaN/GaN channel is mainly dominated by IF and CO phonon modes, and is higher than that in the conventional heterostructures with GaN-channels. Meanwhile, the optimized size and In composition of the composite channel to improve the mobility are also clarified.