Observation of weak localization and phase coherent electron transport in sparsely doped (Zn:Ga)O thin films

Weak localization arising due to disorder and leading to phase coherent electron transport was clearly observed in sparsely doped (Zn:Ga)O thin films grown by pulsed laser deposition. All the Ga doped ZnO ((Zn:Ga)O) thin films have shown metal like behavior with a change in sign of temperature coefficient of resistivity (TCR) in temperature dependent resistivity measurements. This has been explained by considering quantum corrections to conductivity where weak localization contribute significantly which was confirmed by temperature dependent magneto-transport measurements at varying magnetic fields. Phase coherent length as extracted from magneto-transport measurement was found to vary with Ga concentration in the ZnO film. Maximum phase coherent length (at 5 K) was found to be ∼337 nm at Ga concentration ∼ 0.75 at %. By reducing film thickness much below the phase coherent length in (Zn:Ga)O (Ga ∼0.75 at %) film, a clear signature of dimensional crossover of weak localization resulting in phase coherent electron transport along film thickness was observed. Temperature dependence of phase coherent length has suggested electron-electron scattering as the major phase breaking mechanism in the (Zn:Ga)O thin films. Observation of varying phase coherent length with Ga concentration in ZnO film and dimensional crossover of weak localization in ultra thin films may be useful in futuristic phase coherent transport applications based on ZnO.