Improved N-Al codoped p-type ZnO thin films by introduction of a homo-buffer layer

p-type ZnO thin films have been realized by a N-Al codoping method. The influence of homo-buffer layer on film properties was studied in this work. The buffer layer was deposited at a high temperature of 600 °C, and the desired codoped film was successively formed at 500 °C on the first template layer. The N-Al codoped ZnO film was improved evidently in its crystal quality, optical quality and p-type conduction by adopting a homo-buffer layer. Hall measurements revealed that the p-type film had a low resistivity around 8.20 Ω cm. The decrease in resistivity comes from a large increase of mobility (from 0.43 to 2.06 cm2 V−1 s) and a slight increase of carrier concentration (typically about 1017 cm−3). Introduction of a homo-buffer layer is a promising approach to realize p-type ZnO.