Effect of Al Distribution on Carrier Generation of Atomic Layer Deposited Al-Doped ZnO Films

The effect of the Al distribution on the electrical properties of Al-doped ZnO (AZO) films deposited by atomic layer deposition (ALD) is investigated. In order to control the Al distribution, the pulsing time of trimethylaluminum (TMA) is varied from 2 (within an ALD window) to 0.1 s. As a result, the areal density of Al atoms incorporated in a single dopant layer decreases from 3.3 × 10 14 to 1.2 × 10 14 cm −2 . Hall measurements reveal that the minimum resistivity of the ALD-AZO films is decreased from 3.2 × 10 −3 to 1.7 × 10 −3 Ω cm as a result of reducing the TMA pulsing time from 2 to 0.1 s. This decrease is due to the obvious increase of the carrier concentration from 1.4 × 10 20 to 4.7 × 10 20 cm −3 . It is suggested that both the improved doping efficiency (from 13 to 58%) and the insertion of more dopant layers within the ZnO matrix are responsible for the increase of the carrier concentration.