Effects of Ar Vs. O2 Ambient On Pulsed-Laser-Deposited Ga-Doped ZnO

Abstract Ga-doped ZnO films were deposited by pulsed laser deposition (PLD) at 200 °C and 10 mTorr in either pure argon (Ar films) or in oxygen (O 2 films). The bulk resistivity of the Ar films is −4  Ω cm at 300 K, two orders of magnitude lower than that of the O 2 films. In the Ar films, the donor concentration N D as determined by a detailed Hall-effect analysis is close to 100% of the total Ga concentration [Ga] measured by secondary ion mass spectrometry (SIMS), while in the O 2 films N D is less than 50% of [Ga]. Furthermore, the compensation ratio K = N A / N D is >90% for the O 2 films and 2 films have resistivities of about 5×10 −4  Ω cm, approaching those of the Ar films. These results suggest that oxygen-rich environments produce Ga/O complexes that reduce the dopant activation efficiency and thus decrease N D and increase K . Some of these complexes may also contribute to the increase in deep centers observed in photoluminescence.

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