Zinc Oxide Grown by Atomic Layer Deposition: From Heavily n‐Type to p‐Type Material

ZnO grown by atomic layer deposition (ALD) is an interesting material for electronic applications requiring low processing temperature. Herein, it is shown that the electrical conductivity of ZnO ALD films can be varied from 10−1 to 102 Ω−1 cm−1 by moving the growth conditions from oxygen rich to zinc rich, through changing the deposition temperature between 100 and 200 °C. The temperature‐dependent photoluminescence (PL) studies show evidence that shallow defect states in ZnO ALD films are clearly influenced by oxygen‐ and zinc‐rich conditions, which affect the binding energy of existing donors as well as the relative intensity from donor‐ to acceptor‐related luminescence. The films grown at 100 °C, under O‐rich conditions, are more resistive and show considerably more intensive acceptor‐related PL bands than those grown at 200 °C, when Zn‐rich conditions are achieved. Moreover, scaling of electron concentration with the growth temperature is accompanied by a variance of the bandgap due to the Burstein–Moss effect. It is shown that the acceptor‐related conductivity of ZnO ALD can be achieved by nitrogen doping under O‐rich conditions. The related homojunction with the rectification ratio of 4 × 104 (at ± 2 V) is obtained based on ZnO ALD films deposited at 100 °C.