  We provide the first observation of weak localization in high carrier density
two-dimensional electron gas in AlInN/GaN heterostructures; at low temperatures
and low fields the conductivity increases with increasing magnetic field. Weak
localization is further confirmed by the lnT dependence of the zero-field
conductivity and angle dependence of magnetoresistance. The inelastic
scattering rate is linearly proportional to temperature, demonstrating that
electron-electron scattering is the principal phase breaking mechanism.
Shubnikov-de Haas (SdH) oscillations at high magnetic fields are also observed.
From the temperature dependent amplitude of SdH oscillation and Dingle plot,
the effective mass of electron is extracted to be 0.2327me; in addition the
quantum lifetime is smaller than transport time from Hall measurement,
indicating small angle scattering such as from remote ionized impurities is
dominant. Above 20 K, the scattering changes from acoustic phonon to optical
phonon scattering, resulting in a rapid decrease in carrier mobility with
increasing temperature.
