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

The diagonal and nondiagonal components of the transverse magnetoresistance have been measured, over a wide magnetic field range, in modulated doped A l0.25Ga0.75N/GaN heterostructures. The diagonal component shows electron-el ectron interaction in the whole magnetic field range, Shubnikov-de Hass (Sd H) oscillations superimposed at high magnetic field, and weak localization at very low magnetic field. The SdH oscillations are evidence of the existe nce of a two-dimensional electron gas (2DEG) in the heterostructure. Only o ne kind of carriers is present with an electron density of 1.01 x 10(17) m( -2), an effective mass of 0.23m(0) and a quantum scattering time tau(q) = 0 .05 ps. From the diffusive electron-electron interaction, an impurity scatt ering time tau(ee) = 0.044 ps, a Hartree factor F = 0.25 and the Drude scat tering time tau(0) = 0.26 ps, were obtained. The weak localization yields t wo scattering times, an elastic scattering time tau(e) = 0.023 ps independe nt of the temperature, and an inelastic scattering time, tau(i), with a tem perature dependence following the 1/tau(i) proportional to T ln T law expec ted for the impurity contribution of the electron-electron interaction in 2 D. The tau(q)/tau(0) ratio gives the dominant scattering mechanism, which i n our case is 0.19. The remote ionized impurities alone do not explain this obtained ratio, while the introduction of the interface roughness could ex plain it. (C) 2000 American Institute of Physics. [S0021-8979(00)06314-3].