Scattering times in AlGaN/GaN two-dimensional electron gas from magnetoresistance measurements

Abstract

The diagonal and nondiagonal components of the transverse magnetoresistance have been measured, over a wide magnetic field range, in modulated doped Al0.25Ga0.75N/GaN heterostructures. The diagonal component shows electron–electron interaction in the whole magnetic field range, Shubnikov–de Hass (SdH) oscillations superimposed at high magnetic field, and weak localization at very low magnetic field. The SdH oscillations are evidence of the existence of a two-dimensional electron gas (2DEG) in the heterostructure. Only one kind of carriers is present with an electron density of 1.01×1017 m−2, an effective mass of 0.23m0 and a quantum scattering time τq=0.05 ps. From the diffusive electron–electron interaction, an impurity scattering time τee=0.044 ps, a Hartree factor F=0.25 and the Drude scattering time τ0=0.26 ps, were obtained. The weak localization yields two scattering times, an elastic scattering time τe=0.023 ps independent of the temperature, and an inelastic scattering time, τi, with a temperature dependence following the 1/τi∝T ln T law expected for the impurity contribution of the electron–electron interaction in 2D. The τq/τ0 ratio gives the dominant scattering mechanism, which in our case is 0.19. The remote ionized impurities alone do not explain this obtained ratio, while the introduction of the interface roughness could explain it.