Non-monotonic Magnetoresistance in an AlGaN/GaN High-electron-mobility Transistor Structure in the Ballistic Region

Abstract

In this report, we will discuss the nonmonotonic magnetoresistance (MR) in an AlGaN/GaNhigh-electron-mobility transistor (HEMT) in a perpendicular magnetic field B in the ballistic region(kBT /~ > 1) and in the weakly-disordered limit (kF l = 159 1), where kB, T, , ~, kF , and lrepresent the Boltzmann constant, temperature, elastic scattering time, reduced Planck constant,Fermi wave vector and mean free path, respectively. The MR shows a local maximum between theweak localization (WL) and the Shubnikov-de Haas regions. In the low magnetic field regime, thequantum correction to the conductivity is proportional to T−3/2, which is consistent with a recenttheory [T. A. Sedrakyan, and M. E. Raikh, Phys. Rev. Lett. 100, 106806 (2008)]. Accordingto our results, as the temperature is increased, the position of the MR maximum in B increases. These results cannot be explained by present theories. Moreover, in the high-magnetic-field regime,neither the magnetic and nor the temperature dependences of the observed MR is consistent withpresent theories. We, therefore, suggest that while some features of the observed nonmonotonic MRcan be successfully explained, further experimental and theoretical studies are necessary to obtaina thorough understanding of the MR effects.