Atomic Layer Deposition of Undoped and Al-Doped ZnO Thin Films Usingthe Zn Alkoxide Precursor Methylzinc Isopropoxide

Undoped and Al-doped ZnO thin films have been prepared by atomic layer deposition (ALD) using the Zn precursor methylzinc isopropoxide [MZI, (CH3)Zn(OCH(CH3)2)] with water (H2O). Dimethylaluminum isopropoxide (DMAI) was used as an Al precursor. The self-limiting ALD process via alternate surface reactions of MZI and H2O was confirmed by thickness measurements of the ZnO films with varying MZI supply time and numbers of MZI-H2O ALD cycles. Under optimal reaction conditions, the growth rate of the ZnO films was 1.9∼2.0 Å/cycle in the substrate temperature range of 160∼200 °C and the maximum growth rate reached about 2.58 Å/cycle at 240 °C. Room temperature photoluminescence (PL) measurements revealed a strong free excitonic peak at 3.27 eV with almost negligible deep level emission. Resistivities of ZnO films were measured to be 5 × 10−3 ∼3.2 × 10−3 Ωcm depending on the substrate temperature. By Al-doping, the resistivity was minimized to ∼1 35 × 10−4 Ωcm.